Defrosting apparatus for refrigerators and method for controlling the same

ABSTRACT

A defrosting apparatus for a refrigerator and a method for controlling the defrosting apparatus, wherein the refrigerating compartment is cooled irrespective of the internal temperature of the freezing compartment when the internal temperature of the refrigerating compartment is higher than a predetermined temperature, so that the refrigerating compartment is maintained below the predetermined temperature. The defrosting operation is carried out in accordance with the drive times of the compressor and refrigerating compartment fan when the internal temperature of the refrigerating compartment is higher than the predetermined temperature even though the compressor and refrigerating compartment fan are continuously driven. Accordingly, it is possible to improve the cooling efficiency. For the rapid refrigerating operation, the point of time when the defrosting operation for the refrigerating compartment begins is accurately determined by calculating a temperature drop gradient on the basis of a variation in the internal temperature of the refrigerating compartment. For the rapid freezing operation, the point of time when the defrosting operation for the freezing compartment begins is accurately determined by calculating a temperature drop gradient on the basis of a variation in the internal temperature of the freezing compartment. In either case, accordingly, it is possible to efficiently achieve the defrosting operation.

FIELD OF THE INVENTION

The present invention relates to a defrosting apparatus for controllingthe defrosting operation of evaporators respectively associated withfreezing and refrigerating compartments of a refrigerator and a methodfor controlling such a defrosting apparatus.

BACKGROUND OF THE INVENTION

An example of such a defrosting apparatus for refrigerators is disclosedin Japanese Utility Model Laid-open publication No. Sho. 56-149859published on Nov. 10, 1981. The defrosting apparatus disclosed in thispublication includes a tank connected in parallel to an. inlet pipeconnected between evaporators of the refrigerator, an electromagneticvalve disposed in one conduit extending from the tank, and a timeradapted to cut off the supply of power to a compressor of therefrigerator while applying power to a defrosting heater to open theelectromagnetic valve when the operation time of the compressor isaccumulated for a certain period of time.

Another defrosting apparatus is disclosed in Japanese Utility ModelLaid-open publication No. Sho. 56-1082 published on Jan. 7, 1981. Thisdefrosting apparatus includes electric heaters respectively arranged inthe vicinity of a refrigerant inlet port and an evaporator. Above andbeneath the evaporator, temperature switches are disposed to control theelectric heaters, respectively. The temperature switches have the sametemperature set value.

FIG. 1 illustrates a typical refrigerator having a conventionalconstruction whereas FIG. 2 illustrates a refrigerating cycle employedin the refrigerator. As shown in FIG. 1, the refrigerator includes arefrigerator body 1 provided with food storing compartments, namely, afreezing compartment 2 and a refrigerating compartment 3. At the frontportion of the refrigerator body 1, doors 2a and 3a are mounted whichserve to open and close the freezing and refrigerating compartments 2and 3, respectively.

Between the freezing and refrigerating compartments 2 and 3, anevaporator 4 is mounted which carries out a heat exchange between airbeing blown into the freezing and refrigerating compartments 2 and 3 andrefrigerant passing through the evaporator 4, thereby evaporating therefrigerant by latent heat from the air while cooling the air. At therear side of the evaporator 4, a fan 5a is mounted which is rotated by afan motor 5 to circulate the cold air heat-exchanged by the evaporator 4through the freezing and refrigerating compartments 2 and 3.

In order to control the amount of cold air supplied to the refrigeratingcompartment 3, a damper 6 is provided which allows the supply of coldair to the refrigerating chamber 3 or cuts off the supply of cold air inaccordance with the internal temperature of the refrigeratingcompartment 3. A plurality of shelves 7 are separably disposed in boththe freezing and refrigerating compartments 2 and 3 to partition thecompartments into several food storing sections.

At respective rear portions of the freezing and refrigeratingcompartments 2 and 3, duct members 8 and 9 are mounted which guide flowsof the cold air heat-exchanged by the evaporator 4 such that they enterand circulate through the freezing and refrigerating compartments 2 and3. The freezing and refrigerating compartments 2 and 3 have cold airdischarge ports 8a and 9a, respectively. Through the cold air dischargeports 8a and 9a, flows of cold air respectively guided by the ductmembers 8 and 9 after being heat-exchanged by the evaporator 4 areintroduced in the freezing and refrigerating compartments 2 and 3.

A compressor 10 is mounted at the lower portion of the refrigerator body1 to compress the gaseous refrigerant of low temperature and pressure,emerging from the evaporator 4, to that of high temperature andpressure. A defrosted water dish 11 is also disposed at the front side(the left side when viewed in FIG. 1) of the compressor 10. Thedefrosted water dish 11 collects water (dewdrop) produced from the airbeing blown by the fan 5a upon cooling the air by the heat exchange atthe evaporator 4 and water (defrosted water) produced upon defrostingfrost formed at the interior of the refrigerator and drains them out ofthe refrigerator.

An assistant condenser 12 is disposed beneath the defrosted water dish11 to evaporate water collected in the defrosted water dish 11. A maincondenser 13, which has a zig-zag tube shape, is arranged at both sidewalls 1a. upper wall 1b or back wall of the refrigerator body 1. Throughthe main condenser 13, the gaseous refrigerant of high temperature andpressure passes which has been compressed by the compressor 10. Whilepassing through the main condenser 13, the gaseous refrigerant carriesout a heat exchange with ambient air in accordance with the natural orforced convection phenomenon, so that it is forcedly cooled to have aliquid phase under low temperature and high pressure.

At one side of the compressor 10, a capillary tube 14 is mounted. Thecapillary tube 14 serves to abruptly expand the liquid-phase refrigerantof low temperature and high pressure, which has been liquefied in themain condenser 13, thereby reducing the pressure of the refrigerant toan evaporation pressure. By the capillary tube 14, the refrigerant haslow temperature and pressure. Around the front wall of the refrigeratorbody 1, an anti-dewing pipe 15 is disposed to prevent the formation ofdewdrops due to a temperature difference between the ambient warm airand the cold air existing in the refrigerator body 1.

To operate the refrigerator, a user switches on a power switch aftersetting the desired internal temperatures of the freezing refrigeratingcompartments 2 and 3. Once the refrigerator is powered, the internaltemperature of the freezing compartment 2 is sensed by a temperaturesensor installed in the freezing compartment 2. The temperature sensorsends a signal indicative of the sensed temperature to a control unit(not shown) which, in turn, determines whether or not the sensedtemperature is more than a predetermined temperature.

When the internal temperature of the freezing compartment 2 isdetermined as being more than the predetermined temperature, thecompressor 10 and fan motor 5 are driven. With the fan motor 5 beingdriven, the fan 5a is rotated.

With the compressor 10 being driven, the refrigerant is compressed in agaseous phase under high temperature and pressure. This refrigerant isthen fed to the assistant condenser 12. While passing through theassistant condenser 12, the refrigerant evaporates water collected inthe defrosted water dish 11. The refrigerant is then introduced in themain condenser 13. While passing through the main condenser 13, therefrigerant carries out a heat exchange with ambient air in accordancewith the natural or forced convection phenomenon, so that it is cooledto have a liquid phase under low temperature and high pressure.

The liquid-phase refrigerant of low temperature and high pressure, whichhas been liquefied in the main condenser tube 13, enters the anti-dewingpipe 15. While passing through the anti-dewing pipe 15, the refrigerantis changed to a phase with a more or less higher temperature of about 6°to 13° C. As a result, the generation of dewdrops in the refrigerator isprevented. The liquid-phase refrigerant of low temperature and highpressure then passes through the capillary tube 14 which serves toexpand the refrigerant, thereby reducing its pressure to an evaporationpressure. By the capillary tube 14, the refrigerant has low temperatureand pressure. The refrigerant emerging from the capillary tube 14 isthen introduced in the evaporator 4.

While passing through the evaporator 4 which is constituted by aplurality of pipes, the refrigerant of low temperature and pressurecarries out a heat exchange with ambient air. By this heat exchange, therefrigerant is vaporized while cooling the air. The resultant gaseousrefrigerant of low temperature and pressure emerging from the evaporator4 is then introduced in the compressor 10. Thus, the refrigerantcirculates the refrigerating cycle repeatedly, as shown in FIG. 2.

On the other hand, the cold air heat-exchanged with the refrigerant inthe evaporator 4 is blown by a rotating force of the fan 5a and guidedby the duct members 8 and 9 so that it is discharged into the freezingand refrigerating compartments 2 and 3 through the cold air dischargeports 8a and 9a.

By the cold air discharged into the freezing and refrigeratingcompartments 2 and 3 through the cold air discharge ports 8a and 9a, theinternal temperatures of the freezing and refrigerating compartments 2and 3 are gradually reduced to certain levels, respectively.

During the cold air discharging operation, the damper 6 arranged at therear side of the duct member 9 for the refrigerating compartment 3controls the amount of cold air supplied to the refrigeratingcompartment 3 on the basis of the variable internal temperature of therefrigerating compartment 3 so that the refrigerating compartment 3 canbe maintained at an appropriate temperature.

As apparent from the above description, the above-mentioned conventionalrefrigerator uses the control system for controlling the internaltemperatures of the freezing and refrigerating compartments 2 and 3based on the internal temperature of the freezing compartment 2. Thatis, this temperature control is achieved in such a manner that thecompressor 10 and fan motor 5 are driven to circulate cold air throughthe freezing compartment 2 when the internal temperature of the freezingcompartment 2 is higher than a predetermined temperature, while beingstopped to cut off the supply of cold air to the freezing compartment 2when the internal temperature of the freezing compartment 2 is nothigher than the predetermined temperature.

Since only the internal temperature of the freezing compartment 2 isused to control the compressor 10, however, the conventionalrefrigerator involves various problems. For example, the internaltemperature of the freezing compartment may be at a low level even whenthe internal temperature of the refrigerating compartment is abruptlyincreased over its predetermined level due to the overload state of therefrigerating compartment or an increased number of times opening therefrigerating compartment door. In this case, the compressor 10 is notdriven. As a result, the internal temperature of the refrigeratingcompartment 3 is continuously increased, so that food stored in therefrigerating compartment may spoil easily. Therefore, there is adegradation in reliability.

In the conventional evaporator including the single evaporator 4 and thesingle fan 5a, moisture existing in air being blown by the fan 5a isfrosted on the evaporator 4 when the air is cooled by the refrigerantpassing through the evaporator 4.

In order to defrost the frost formed on the evaporator 4, power isapplied to a heater (not shown). When the heater is heated, the frost onthe evaporator 4 is melted and then drained to the defrosted water dish11 disposed at the lower portion of the refrigerator body 1.

Although a more or less amount of frost formed on the evaporator isremoved by melting it in the above-mentioned refrigerator, defrostedwater produced between adjacent pins of the evaporator is still attachedon the evaporator 4 because of its cohesion. This defrosted water isfrozen by the cold air heat-exchanged at the evaporator by the lapse oftime, thereby degrading the heat exchanging ability of the evaporator.Furthermore, the evaporator itself may be frozen. In this case, theevaporator may be damaged.

In order to solve such problems, another refrigerator have recently beenproposed which has an arrangement including evaporators respectivelyassociated with freezing and refrigerating compartments so that thedefrosting operation for removing frost formed on the evaporators can beindividually carried out for the evaporators. In this case, thedefrosting operation can be efficiently achieved because it isindividually carried out for the evaporators. However, the period oftime that the compressor is being stopped increases because thedefrosting operations for the freezing and refrigerating compartmentsare carried out sequentially. For this reason, it is difficult tomaintain the refrigerating compartment below a certain temperature.

SUMMARY OF THE INVENTION

Therefore, an object of the invention is to solve the above-mentionedproblems and to provide a defrosting apparatus for a refrigerator and amethod for controlling the defrosting apparatus, wherein therefrigerating compartment is cooled irrespective of the internaltemperature of the freezing compartment when the internal temperature ofthe refrigerating compartment is higher than a predeterminedtemperature, so that the refrigerating compartment is maintained belowthe predetermined temperature.

Another object of the invention is to provide a defrosting apparatus fora refrigerator and a method for controlling the defrosting apparatus,wherein the defrosting operation is carried out in accordance with thedrive times of the compressor and refrigerating compartment fan when theinternal temperature of the refrigerating compartment is higher than thepredetermined temperature even though the compressor and refrigeratingcompartment fan are continuously driven, so that the cooling efficiencycan be improved.

Another object of the invention is to provide a defrosting apparatus fora refrigerator and a method for controlling the defrosting apparatus,wherein the point of time when the defrosting operation begins isdetermined on the basis of the environmental temperature condition, sothat the defrosting operation can be efficiently achieved.

Another object of the invention is to provide a defrosting apparatus fora refrigerator and a method for controlling the defrosting apparatus,wherein the defrosting operation for the freezing compartment is delayedwhen the defrosting operation for the refrigerating compartment isachieved within a predetermined time under the defrost requiringcondition of the freezing compartment so that the defrosting operationsfor the freezing and refrigerating compartments can be simultaneouslycarried out.

Another object of the invention is to provide a defrosting apparatus fora refrigerator and a method for controlling the defrosting apparatus,wherein the defrosting operations for the freezing and refrigeratingcompartments are simultaneously carried out irrespective of the defrostrequiring condition of the refrigerating compartment when the freezingcompartment is under the defrost requiring condition, so that therefrigerating efficiency can be improved.

Another object of the invention is to provide a defrosting apparatus fora refrigerator and a method for controlling the defrosting apparatus,wherein the defrosting operations for the freezing and refrigeratingcompartments are simultaneously carried out irrespective of the defrostrequiring condition of the freezing compartment when the refrigeratingcompartment is under the defrost requiring condition, so that therefrigerating efficiency can be improved.

Another object of the invention is to provide a defrosting apparatus fora refrigerator and a method for controlling the defrosting apparatus,wherein for the rapid refrigerating operation, the point of time whenthe defrosting operation for the refrigerating compartment begins isaccurately determined by calculating a temperature drop gradient on thebasis of a variation in the internal temperature of the refrigeratingcompartment, so that the defrosting operation can be efficientlyachieved.

Another object of the invention is to provide a defrosting apparatus fora refrigerator and a method for controlling the defrosting apparatus,wherein for the rapid freezing operation, the point of time when thedefrosting operation for the freezing compartment begins is accuratelydetermined by calculating a temperature drop gradient on the basis of avariation in the internal temperature of the freezing compartment, sothat the defrosting operation can be efficiently achieved.

In accordance with one aspect, the present invention provides anapparatus for defrosting a refrigerator, comprising: a refrigeratingcompartment for storing food to be refrigerated; a freezing compartmentadapted to store food to be frozen, the freezing compartment beingdefined above the refrigerating compartment by an intermediate partitionmember; a compressor adapted to compress a refrigerant to that of hightemperature and pressure under a control of compressor driving means; apair of heat exchanging means respectively associated with the freezingand refrigerating compartments and adapted to heat-exchange flows ofair, being blown into the freezing and refrigerating compartments, withthe refrigerant, thereby cooling the air flows; a pair of fan meansrespectively associated with the freezing and refrigerating compartmentsand adapted to supply the cold air flows heat-exchanged with the heatexchanging means to the freezing and refrigerating compartments under acontrol of fan motor driving means; a pair of heating means respectivelyassociated with the freezing and refrigerating compartments and adaptedto defrost the freezing and refrigerating compartment heat exchangingmeans under a control of heater driving means; temperature sensing meansadapted to sense respective internal temperatures of the freezing andrefrigerating compartments; temperature setting means adapted to setrespective desired temperatures of the freezing and refrigeratingcompartments, the temperature setting means also setting a rapidfreezing operation and a rapid refrigerating operation; control meansadapted to determine the point of time when a defrosting operation foreach heat exchanging means begins on the basis of a drive time of thecompressor and respective drive times of the freezing and refrigeratingcompartment fan means, the control means also calculating gradients ofrespective internal temperatures of the freezing and refrigeratingcompartments, thereby determining defrost requiring conditions of thefreezing and refrigerating compartments; and conduit temperature sensingmeans adapted to sense respective conduit temperatures of the freezingand refrigerating compartment heat exchanging means during respectiveheat generating operations of the freezing and refrigerating compartmentheating means.

In accordance with another aspect, the present invention provides amethod for controlling a defrosting operation of a refrigerator,comprising: temperature setting step of setting respective desiredtemperature of freezing and refrigerating compartments by freezing andrefrigerating compartment temperature setting means; normal operationstep of lowering respective internal temperatures of the freezing andrefrigerating compartments to the desired temperatures set at thetemperature setting step in accordance with driving of a compressor anddriving of freezing and refrigerating compartment fan means; freezingcompartment temperature determining step of determining whether or notthe internal temperature of the freezing compartment is higher than itsdesired temperature set by the freezing compartment temperature settingmeans; refrigerating compartment temperature determining step of drivingthe compressor when the internal temperature of the freezing compartmentis determined at the freezing compartment temperature determining stepas being higher than its desired temperature and then determiningwhether or not the internal temperature of the refrigerating compartmentis higher than its desired temperature set by the refrigeratingcompartment temperature setting means; refrigerating compartment fanmeans driving step of driving refrigerating compartment fan means whenthe internal temperature of the refrigerating compartment is determinedat the refrigerating compartment temperature determining step as beinghigher than its desired temperature set by the refrigerating compartmenttemperature setting means, thereby lowering the internal temperature ofthe refrigerating compartment; refrigerating compartment fan meansstopping step of stopping the refrigerating compartment fan means whenthe internal temperature of the refrigerating compartment is determinedat the refrigerating compartment temperature determining step as beinglower than its desired temperature set by the refrigerating compartmenttemperature setting means; freezing compartment fan means driving stepof driving the freezing compartment fan means when the internaltemperature of the refrigerating compartment is lower than its desiredtemperature set by the refrigerating compartment temperature settingmeans after executing both the refrigerating compartment fan meansdriving and stopping steps; refrigerating compartment temperaturesensing step of stopping both the compressor and the freezingcompartment fan means when the internal temperature of the freezingcompartment is lower than its desired temperature set by the freezingcompartment temperature setting means, and then sensing the internaltemperature of the refrigerating compartment; refrigerating compartmenttemperature determining step of determining whether or not the internaltemperature of the refrigerating compartment sensed at the refrigeratingcompartment temperature sensing step is higher than a predeterminedtemperature stored in control means; time elapse determining step ofdetermining whether or not the refrigerating compartment a predeterminedtime has elapsed under a condition that the internal temperature of therefrigerating compartment is higher than the predetermined temperature;drive time counting step of driving both the compressor and therefrigerating compartment fan means when it is determined at the timeelapse determining step that the predetermined time has elapsed, andthen counting the drive time of the refrigerating compartment fan means;drive time determining step of determining whether or not the drive timeof the refrigerating compartment fan means counted at the drive timecounting step is more than a predetermined time stored in the controlmeans; total drive time determining step of clearing the counted drivetime of the refrigerating compartment fan means when the drive time ofthe refrigerating compartment fan means is determined at the drive timedetermining step as being less than the predetermined time stored in thecontrol means, and then determining whether or not the total drive timeof the compressor is more than a predetermined total drive time storedin the control unit; heating step of driving refrigerating compartmentevaporator heating means when the total drive time is determined at thetotal drive time determining step as being more than the predeterminedtotal drive time, thereby defrosting a refrigerating compartmentevaporator; refrigerating compartment conduit temperature sensing stepof sensing a conduit temperature of the refrigerating compartmentevaporator while the refrigerating compartment evaporator heating meansis generating heat; and refrigerating compartment conduit temperaturedetermining step of determining whether or not the conduit temperatureof the refrigerating compartment evaporator sensed at the refrigeratingcompartment conduit temperature sensing step is higher than apredetermined conduit temperature stored in the control means.

In accordance with another aspect, the present invention provides amethod for controlling a defrosting operation of a refrigerator,comprising: drive time calculating step of calculating a drive time of acompressor and respective drive times of freezing and refrigeratingcompartment fan means; defrost requiring condition determining step ofdetermining respective defrost requiring conditions of freezing andrefrigerating compartment evaporators on the basis of the drive time ofthe compressor and the drive times of the freezing and refrigeratingcompartment fan means all calculated at the drive time calculating step;defrosting operation step of executing a defrosting operation forremoving frost formed on the freezing and refrigerating compartmentevaporators in accordance with the defrost requiring conditions of thefreezing and refrigerating compartment evaporators determined at thedefrost requiring condition determining step; and defrosting enddetermining step of sensing respective conduit temperatures of thefreezing and refrigerating compartment evaporators being varied duringthe defrosting operation executed at the defrosting operation step, anddetermining whether or not the frost on the freezing and refrigeratingcompartment evaporators has been completely removed on the basis of thesensed conduit temperatures.

In accordance with another aspect, the present invention provides amethod for controlling a defrosting operation of a refrigerator,comprising: refrigerating compartment fan means's drive time calculatingstep of calculating a drive time of refrigerating compartment fan meansin accordance with an operation mode of the refrigerator being variablewhen the refrigerating compartment fan is driven; refrigeratingcompartment evaporator's defrost requiring condition determining step ofdetermining a defrost requiring condition of a refrigerating compartmentevaporator on the basis of the drive time of the refrigeratingcompartment fan means calculated at the refrigerating compartment fanmeans's drive time calculating step; freezing compartment fan means'sdrive time calculating step of calculating a drive time of freezingcompartment fan means when the freezing compartment fan is driven inaccordance with the internal temperature of the freezing compartment;freezing compartment evaporator's defrost requiring conditiondetermining step of determining a defrost requiring condition of afreezing compartment evaporator on the basis of the drive time of thefreezing compartment fan means calculated at the freezing compartmentfan means's drive time calculating step; and simultaneous defrostingoperation step of simultaneously executing defrosting operations forremoving frost formed on the freezing and refrigerating compartmentevaporators when the refrigerating compartment evaporator is determinedas being under the defrost requiring condition at the refrigeratingcompartment evaporator's defrost requiring condition determining step.

In accordance with another aspect, the present invention provides amethod for controlling a defrosting operation of a refrigerator,comprising: initial temperature sensing step of sensing an initialinternal temperature of a refrigerating compartment when a rapid coolingoperation is executed; rapid refrigerating operation step of driving thecompressor and the refrigerating compartment fan means, therebyexecuting a rapid refrigerating operation for the refrigeratingcompartment; temperature sensing step of sensing an internal temperatureof the refrigerating compartment being varied at sampling time intervalswhile counting the drive time of the refrigerating compartment fanmeans; temperature variation calculating step of calculating atemperature drop gradient corresponding to a variation in the internaltemperature of the refrigerating compartment on the basis of thetemperature sensed at the temperature sensing step and the initialtemperature sensed at the initial temperature sensing step; defrostbeginning point determining step of determining a point of time when adefrosting operation for a refrigerating compartment evaporator beginson the basis of the temperature variation calculated at the temperaturevariation calculating step; and defrosting operation step of executingthe defrosting operation of the refrigerating compartment evaporator inaccordance with the defrost beginning point determined at the defrostbeginning point determining step.

In accordance with another aspect, the present invention provides amethod for controlling a defrosting operation of a refrigerator,comprising: normal operation step of executing a cooling operation bydriving a compressor on the basis of an internal temperature of afreezing compartment and by controlling refrigerating compartment fanmeans on the basis of respective internal temperatures of freezing andrefrigerating compartments being varied; compartment temperature sensingstep of sensing the internal temperatures of the freezing andrefrigerating compartments being varied during the cooling operationexecuted at the normal operation step; abnormal temperature determiningstep of determining whether the freezing and refrigerating compartmentsare in abnormal temperature states, respectively, on the basis of theinternal temperatures of the freezing and refrigerating compartmentssensed at the compartment temperature sensing step; abnormal coolingoperation step of cooling the freezing and refrigerating compartmentswhen the freezing and refrigerating compartments are determined at theabnormal temperature determining step as being in abnormal temperaturestates, respectively; cooling temperature sensing step of sensingrespective internal temperatures of the freezing and refrigeratingcompartments being varied upon driving the freezing and refrigeratingcompartment fan means along with the compressor; defrost beginning pointdetermining step of determining respective points of time whendefrosting operations for freezing and refrigerating compartmentevaporators begin, on the basis of respective drive times of thefreezing and refrigerating compartment fan means along with the drivetime of the compressor, when the internal temperatures of the freezingand refrigerating compartments sensed at the cooling temperature sensingstep are higher than predetermined temperatures respectively stored incontrol means; and defrosting operation step of executing the defrostingoperations for the freezing and refrigerating compartment evaporatorsrespectively in accordance with the defrost beginning points determinedat the defrost beginning point determining step.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and aspects of the invention will become apparent from thefollowing description of embodiments with reference to the accompanyingdrawings in which:

FIG. 1 is a partially-broken perspective view illustrating aconventional refrigerator;

FIG. 2 is a circuit diagram illustrating a refrigerating cycle employedin the conventional refrigerator;

FIG. 3 is a sectional view illustrating a refrigerator to which adefrosting apparatus according to the present invention is applied;

FIG. 4 is a circuit diagram illustrating a refrigerating cycle accordingto the present invention;

FIG. 5 is a block diagram illustrating the defrosting apparatusaccording to the present invention;

FIGS. 6A to 6C are flow charts respectively illustrating the sequence ofa method for controlling the defrosting operation of the refrigerator inaccordance with a first embodiment of the present invention;

FIGS. 7A to 7C are flow charts respectively illustrating the sequence ofa method for controlling the defrosting operation of the refrigerator inaccordance with a second embodiment of the present invention;

FIGS. 8A and 8B are flow charts respectively illustrating the sequenceof a method for controlling the defrosting operation of the refrigeratorin accordance with a third embodiment of the present invention; and

FIGS. 9A to 9B are flow charts respectively illustrating the sequence ofa method for controlling the defrosting operation of the refrigerator inaccordance with a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3 illustrates a refrigerator to which a defrosting apparatusaccording to the present invention is applied. On the other hand, FIG. 4illustrates a refrigerating cycle employed in the refrigerator.

As shown in FIG. 3, the refrigerator includes a refrigerator body 20which is vertically divided into two compartments, namely, a freezingcompartment 22 and a refrigerating compartment 24 by an intermediatewall member 21. At the front portion of the refrigerator body 20, doors22a and 24a are mounted which serve to open and close the freezing andrefrigerating compartments 22 and 24, respectively.

The freezing and refrigerating compartments 22 and 24 serve as foodstoring compartments, respectively.

At the rear portion of the freezing compartment 22, a freezingcompartment evaporator 26 is mounted which carries out a heat exchangebetween air being blown into the freezing compartment 22 and therefrigerant passing through the first evaporator 26, thereby evaporatingthe refrigerant by latent heat from the air while cooling the air. Afreezing compartment fan 30 is arranged above the freezing compartmentevaporator 26. The freezing compartment fan 30 is driven by a freezingcompartment fan motor 28 to circulate the cold air heat-exchanged by thefreezing compartment evaporator 26 in the freezing compartment 22.

At the front of the freezing compartment evaporator 26, namely, at therear of the freezing compartment 22, a freezing compartment duct member32 is disposed which serves to guide a flow of cold air heat-exchangedby the freezing compartment evaporator 26 such that it circulatesthrough the freezing compartment 22 by the rotating force of thefreezing compartment fan 30. The freezing compartment duct member 32 isprovided with an air discharge port 32a through which the cold airguided by the freezing compartment duct member 32 after beingheat-exchanged by the freezing compartment evaporator 26 is introducedin the freezing compartment 22.

A heater 33 is disposed beneath the freezing compartment evaporator 26.The heater 33 generates heat to remove frost formed on the freezingcompartment evaporator 26 when air being blown by the freezingcompartment fan 30 is cooled by refrigerant passing through the freezingcompartment evaporator 26.

A defrosted water dish 34 is disposed beneath the heater 33 provided forthe freezing compartment evaporator 26. The defrosted water dish 34collects defrosted water and subsequently drains the collected waterthrough a drain hose 52 to an evaporating dish 54 disposed at the bottomof the refrigerator body 20. A thermistor 36 is disposed at the frontside of the freezing compartment fan 30 to sense the internaltemperature Tf of the freezing compartment 22. The thermistor 36constitutes a freezing compartment temperature sensing unit 111 of atemperature sensing unit 110 included in the defrosting apparatus whichwill be described hereinafter.

On the other hand, a refrigerating compartment evaporator 40 is mountedat the rear side of the refrigerating compartment 24. The refrigeratingcompartment evaporator 40 carries out a heat exchange between air beingblown into the refrigerating compartment 24 and the refrigerant passingthrough the refrigerating compartment evaporator 40, thereby evaporatingthe refrigerant by latent heat from the air while cooling the air. Abovethe refrigerating compartment evaporator 40, a refrigerating compartmentfan 44 is rotatably mounted to the rotating shaft of a fan motor 42. Therefrigerating compartment fan 44 is driven to circulate the cold airheat-exchanged by the refrigerating compartment evaporator 40 in therefrigerating compartment 24.

At the front of the refrigerating compartment evaporator 40, arefrigerating compartment duct member 46 is disposed which serves toguide a flow of cold air heat-exchanged by the refrigerating compartmentevaporator 40 such that it circulates through the refrigeratingcompartment 24 by the rotating force of the refrigerating compartmentfan 44. The refrigerating compartment duct member 46 is provided with anair discharge port 46a. Through the air discharge port 46a, the cold airguided by the refrigerating compartment duct member 46 is introduced inthe refrigerating compartment 24.

Another heater 47 is disposed beneath the refrigerating compartmentevaporator 40. The heater 47 generates heat to remove frost formed onthe refrigerating compartment evaporator 40 when air being blown by therefrigerating compartment fan 44 is cooled by refrigerant passingthrough the refrigerating compartment evaporator 40.

Another dewdrop dish 48 is disposed beneath the heater 47 provided forthe refrigerating compartment evaporator 40. The dewdrop dish 48collects defrosted water and subsequently drains the collected waterthrough the drain hose 52 to the evaporating dish 54 disposed at thebottom of the refrigerator body 20. Another thermistor 50 is disposed atthe front of the refrigerating compartment duct member 46 to sense theinternal temperature Tr of the refrigerating compartment 24. Thethermistor 50 constitutes a refrigerating compartment temperaturesensing unit 112 of the temperature sensing unit 110 which will bedescribed hereinafter.

A compressor 56 is mounted at the lower portion of the refrigerator body20 to compress the gaseous refrigerant of low temperature and pressure,emerging from the freezing and refrigerating compartment evaporators 26and 40, to that of high temperature and pressure. A main condenser 58 isarranged at the rear portion of the refrigerator body 20. Through themain condenser 58, the gaseous refrigerant of high temperature andpressure passes which has been compressed by the compressor 56. Whilepassing through the main condenser 58, the gaseous refrigerant carriesout a heat exchange with ambient air in accordance with the natural orforced convection phenomenon, so that it is forcedly cooled to have aliquid phase under low temperature and high pressure.

An assistant condenser 60 is arranged beneath the evaporating dish 54 toevaporate water collected in the evaporating dish 54. A plurality ofshelves 62 are disposed in both the freezing and refrigeratingcompartments 22 and 24 to partition the compartments into several foodstoring sections.

In the refrigerator having the above-mentioned arrangement, therefrigerant circulates through the refrigerating cycle shown in FIG. 4.That is, the refrigerant of high temperature and pressure compressed bythe compressor 56 is fed to the assistant condenser 60. While passingthrough the assistant condenser 60, the refrigerant heats watercollected in the evaporating dish 54, thereby evaporating the collectedwater. The refrigerant from the assistant condenser 60 is thenintroduced in the main condenser 58. While passing through the maincondenser 58, the refrigerant of high temperature and pressure is cooledso that it can be liquefied into that of low temperature and pressure.The refrigerant emerging from the main condenser 58 then passes throughthe capillary tube 57 which reduces the pressure of the refrigerant. Therefrigerant is then returned to the compressor 56 after passing throughthe freezing and refrigerating compartment evaporators 26 and 40.

Now, the defrosting apparatus of the present invention, which is appliedto the refrigerator having the above-mentioned arrangement, will bedescribed in detail.

FIG. 5 is a block diagram illustrating the defrosting apparatusaccording to the present invention.

As shown in FIG. 5, the defrosting apparatus includes a DC power supplyunit 90 for converting a source voltage from a commercial AC powersource, input at an AC power input stage (not shown), into a DC voltagewith a voltage level required to drive various units of therefrigerator.

A temperature setting unit 100 is also provided, which is a key switchmanipulated by a user to set desired internal temperatures Tfs and Trsof the freezing and refrigerating compartments. The temperature settingunit 100 includes a freezing compartment temperature setting unit 101adapted to set the desired internal temperature Tfs of the freezingcompartment 22 and a refrigerating compartment temperature setting unit102 adapted to set the desired internal temperature Trs of therefrigerating compartment 24. The freezing compartment temperaturesetting unit 101 is also used to select a rapid freezing operationwhereas the refrigerating compartment temperature setting unit 102 isalso used to select a rapid refrigerating operation.

The temperature sensing unit 110, which is also included in thedefrosting apparatus, serves to sense respective internal temperaturesTf and Tr of the freezing and refrigerating compartment 22 and 24. Thistemperature sensing unit 110 includes a freezing compartment temperaturesensing unit 111 which comprises the thermistor 36 to sense the internaltemperature Tf of the freezing compartment 22 and a refrigeratingcompartment temperature sensing unit 112 which comprises the thermistor50 to sense the internal temperature Tr of the refrigerating compartment24.

The defrosting apparatus also includes a control unit 120 which is amicrocomputer. The control unit 120 receives the DC voltage from the DCpower supply unit 90 and then initializes the refrigerator. The controlunit 120 also receives output signals from the temperature sensing unit110 indicative of respective sensed internal temperatures Tf and Tr ofthe freezing and refrigerating compartments 22 and 24 and determineswhether or not the sensed internal temperatures Tf and Tr are higherthan the desired temperatures Tfs and Trs set by the temperature settingunit 100. On the basis of the determined result, the control unit 120controls the overall operation of the refrigerator. The control unit 120also controls the defrosting operation for the freezing andrefrigerating compartments 22 and 24. For this control, the control unit120 determines the time required to defrost the freezing andrefrigerating compartment evaporators 26 and 40 on the basis of thedrive time of the compressor 56 and respective drive times of thefreezing and refrigerating compartment fans 30 and 44, respectiveinternal temperatures Tf and Tr of the freezing and refrigeratingcompartments 22 and 24 and change of the operation mode of therefrigerator (in particular, the change between the overload operationmode and the normal operation mode).

To control the defrosting operation for the freezing and refrigeratingcompartments 22 and 24 during the rapid freezing operation for thefreezing compartment 22 or during the rapid refrigerating operation forthe refrigerating compartment 24, the control unit 120 also determineswhether or not the freezing and refrigerating compartment evaporators 26and 40 have been frosted, on the basis of respective temperaturegradients Ta of the compartment temperatures Tf and Tr.

A heater driving unit 130 is coupled to the control unit 120 The heaterdriving unit 130 serves to drive the heaters 33 and 47 respectivelyassociated with the freezing and refrigerating compartment evaporators26 and 40 under a control of the control unit 120 in order to defrostthe evaporators 26 and 40. The heater driving unit 130 drives theheaters 33 and 47 when the control unit 120 determines the defrostrequiring condition of the freezing and refrigerating compartmentevaporators 26 and 40 on the basis of the drive time of the compressor56 and respective drive times of the freezing and refrigeratingcompartment fans 30 and 44, respective internal temperatures Tf and Trof the freezing and refrigerating compartments 22 and 24, and respectivetemperature gradients Ta of the compartment temperatures Tf and Troccurring during the rapid freezing or refrigerating operation. Theheater driving unit 130 includes a freezing compartment heater drivingunit 131 for driving the freezing compartment evaporator's heater 33disposed beneath the freezing compartment evaporator 26 to remove frostformed on the freezing compartment evaporator 26 under a control of thecontrol unit 120, and a refrigerating compartment heater driving unit132 for driving the refrigerating compartment evaporator's heater 47disposed beneath the refrigerating compartment evaporator 40 to removefrost formed on the refrigerating compartment evaporator 40 under acontrol of the control unit 120.

The defrosting apparatus further includes a conduit temperature sensingunit 140 for sensing respective temperatures P1 and P2 of the conduitsof the freezing and refrigerating compartment evaporators 26 and 40,namely, respective temperatures of refrigerant flows passing through theevaporators 26 and 40 during the driving of the heaters 33 and 47 andthen sending the resultant conduit temperature data to the control unit120 so that the control unit 120 can determine the stoppage of thedefrosting operations for the evaporators 26 and 40. The conduittemperature sensing unit 140 includes a freezing compartment conduittemperature sensing unit 141 for sensing the conduit temperature P1 ofthe freezing compartment evaporator 26 being varied during the drivingof the freezing compartment evaporator's heater 33 and sending theresultant data indicative of the sensed conduit temperature P1 to thecontrol unit 120, and a refrigerating compartment conduit temperaturesensing unit 142 for sensing the conduit temperature P2 of therefrigerating compartment evaporator 40 being varied during the drivingof the refrigerating compartment evaporator's heater 47 and sending theresultant data indicative of the sensed conduit temperature P2 to thecontrol unit 120.

A compressor driving unit 150 is also coupled to the control unit 120.The compressor driving unit 150 receives a control signal from thecontrol unit 120 generated on the basis of a difference between thedesired compartment temperature Tfs or Trs set by the user through thetemperature setting unit 100 and the compartment temperature Tf or Trsensed by the temperature sensing unit 110. In accordance with thecontrol signal, the compressor driving unit 150 controls the compressor56 to execute the cooling operation for the refrigerator.

In FIG. 5, the reference numeral 160 denotes a fan motor driving unitwhich serves to control the freezing and refrigerating compartment fanmotors 28 and 42 under a control of the control unit 120 such thatrespective internal temperatures Tf and Tr of the freezing andrefrigerating compartments 22 and 24 are maintained at their desiredlevels set by the user. As shown in FIG. 5, the fan motor driving unit160 includes a freezing compartment fan motor driving unit 161 adaptedto control the freezing compartment fan motor 28, which circulates thecold air heat-exchanged by the freezing compartment evaporator 26, undera control of the control unit 120 to maintain the internal temperatureTf of the freezing compartment 22 sensed by the freezing compartmenttemperature sensing unit 111 at its desired level Tfs set by the user,and a refrigerating compartment fan motor driving unit 162 adapted tocontrol the refrigerating compartment fan motor 42, which circulates thecold air heat-exchanged by the refrigerating compartment evaporator 40,under a control of the control unit 120 to maintain the internaltemperature Tr of the refrigerating compartment 24 sensed by therefrigerating compartment temperature sensing unit 112 at its desiredlevel Trs set by the user.

The operation of the defrosting apparatus having the above-mentionedarrangement for controlling the defrosting operation of the refrigeratorwill now be described.

FIGS. 6A to 6C are flow charts respectively illustrating the sequence ofa method for controlling the defrosting operation of the refrigerator inaccordance with a first embodiment of the present invention.

Once the refrigerator is powered, the DC power supply unit 90 converts asource voltage received from a commercial AC power source at the ACpower input stage (not shown) into a DC voltage with a voltage levelrequired to drive various units of the refrigerator. The DC voltage fromthe DC power supply unit 90 is then applied to the control unit 120 aswell as various driving circuits.

At step S1 of FIG. 6A, the control unit 120 initializes the refrigeratorin response to the DC voltage received from the DC power supply unit 90in order to operate the refrigerator. At step S2, the desired internaltemperatures Tfs and Trs of the freezing and refrigerating compartments22 and 24 are set using the freezing and refrigerating compartmenttemperature setting units 101 and 102 of the temperature setting unit100.

The procedure then proceeds to step S3 to drive the compressor 56.Subsequently, the refrigerating compartment fan 44 and freezingcompartment fan 30 are driven at step S4. At step S5, it is thendetermined whether or not the internal temperature Tr of therefrigerating compartment 24 sensed by the refrigerating compartmenttemperature sensing unit 112 is higher than the desired temperature Trsset in the control unit 120.

When the internal temperature Tr of refrigerating compartment 24 isdetermined at step S5 as being higher than the desired temperature Trs(namely, if YES), the procedure proceeds to step S6. At step S6, therefrigerating compartment fan 44 is continuously driven to lower theinternal temperature of the refrigerating compartment 24. On the otherhand, when the internal temperature Tr of refrigerating compartment 24is determined at step S5 as being lower than the desired temperature Trs(namely, if NO), the procedure proceeds to step S7 to stop therefrigerating compartment fan 44.

Where the compressor 56 and refrigerating compartment fan 44 are drivenwhile the freezing compartment fan 30 is being stopped, only therefrigerating compartment evaporator 40 can carry out a heat exchangebetween refrigerant and ambient air. That is, refrigerant compressed toa gaseous phase of high temperature and pressure is discharged out ofthe compressor 56 toward the assistant condenser 60. While passingthrough the assistant condenser 60, the refrigerant evaporates watercollected in the evaporating dish 54. The refrigerant is then introducedin the main condenser 58. While passing through the main condenser 58,the refrigerant carries out a heat exchange with ambient air inaccordance with the natural or forced convection phenomenon, so that itis cooled to have a liquid phase under low temperature and highpressure. That is, the refrigerant is liquefied.

The liquid-phase refrigerant of low temperature and high pressure, whichhas been liquefied in the main condenser 58, then passes through thecapillary tube 57. By the capillary tube 57, the refrigerant is changedto that of low temperature and pressure so that it can be easilyevaporated. The refrigerant emerging from the capillary tube 57 is thenintroduced in the freezing and refrigerating compartment evaporators 26and 40.

While passing through the freezing and refrigerating compartmentevaporators 26 and 40, each of which is constituted by a plurality ofpipes, the refrigerant of low temperature and pressure carries out aheat exchange with air being blown into the freezing and refrigeratingcompartments 22 and 24. By this heat exchange, the refrigerant isvaporized while cooling the air. The resultant gaseous refrigerant flowsof low temperature and pressure respectively emerging from the freezingand refrigerating compartment evaporators 26 and 40 are then introducedin the compressor 56. Thus, the refrigerant circulates the refrigeratingcycle of FIG. 4 repeatedly.

In the above case, however, there is no flow of air being blown towardthe freezing compartment 22 because the freezing compartment fan 30 isnot driven. Accordingly, no heat exchange is carried out at the freezingcompartment evaporator 26. The heat-exchange is carried out only at therefrigerating compartment evaporator 40.

The cold air heat-exchanged with the refrigerant by the refrigeratingcompartment evaporator 40 is blown by the rotating force of therefrigerating compartment fan 44 and guided by the refrigeratingcompartment duct member 46 so that it is discharged into therefrigerating compartment 24 through the cold air discharge port 46a. Asa result, the refrigerating compartment 24 is cooled.

On the other hand, where the freezing compartment fan 30 is driven alongwith the compressor 56, thereby carrying out the cooling operation forthe freezing compartment 22 for a certain period of time, the internaltemperature Tf of the freezing compartment 22 is gradually lowered. Thisinternal temperature Tf of the freezing compartment 22 is sensed by thefreezing compartment temperature sensing unit 111 of the temperaturesensing unit 110. The resultant sensing signal from the freezingcompartment temperature sensing unit 111 is then applied to the controlunit 120.

At step S8, it is then determined whether or not the internaltemperature Tf of the freezing compartment 22 sensed by the freezingcompartment. temperature sensing unit 111 is lower than the desiredtemperature Tfs.

When the internal temperature Tf of the freezing compartment 22 isdetermined at step S8 as being higher than the desired temperature Tfs(namely, if NO), the procedure returns to step S3. The procedure is thenrepeated from step S3 to continuously cool the freezing compartment 22.On the other hand, when the internal temperature Tf of the freezingcompartment 22 is determined at step S8 as being lower than the desiredtemperature Tfs (namely, if YES), the procedure proceeds to step S9 ofFIG. 6B. At step S9, the control unit 120 applies a control signal forstopping the cooling operation for the freezing compartment 22 to boththe compressor driving unit 150 and the freezing compartment fan motordriving unit 161 of fan motor driving unit 160.

Accordingly, the compressor driving unit 150 stops the compressor 56under the control of the control unit 120. The freezing compartment fanmotor driving unit 161 also stops the freezing compartment fan motor 28under the control of the control unit 120, thereby stopping the freezingcompartment fan 30. As a result, the cooling operation for the freezingcompartment 22 is completed.

As mentioned above, the compressor 56 is controlled in accordance withthe internal temperature of the freezing compartment 22. When thecompressor 56 is initially driven, the refrigerating compartment fan 44is first driven. The refrigerating compartment fan 44 is controlled inaccordance with the internal temperature of the refrigeratingcompartment 24 so that the refrigerating compartment 24 can bemaintained at the desired temperature Trs. Once the internal temperatureTr of the refrigerating compartment 24 reaches the desired temperatureTrs, the refrigerating compartment fan 44 is stopped, thereby completingthe cooling operation for the refrigerating compartment 24. At the sametime, the freezing compartment fan 30 is driven. The compressor 56 andfreezing compartment fan 30 are continuously driven until the internaltemperature Tf of the freezing compartment 22 reaches the desiredtemperature Tfs.

Once the internal temperature Tf of the freezing compartment 22 reachesthe desired temperature Tfs, the compressor 56 and freezing compartmentfan 30 are stopped to prevent the freezing compartment 22 from being inan over-freezing state.

In the normal operation mode for executing the freezing operation forthe freezing compartment 22 and the refrigerating operation for therefrigerating compartment 24, the procedure then proceeds to step S10 tosense an abnormal temperature of the refrigerating compartment 24. Atstep S10, the refrigerating compartment temperature sensing unit 112 ofthe temperature sensing unit 110 senses the internal temperature Tr ofthe refrigerating compartment 24 and sends the resultant data to thecontrol unit 120.

It is then determined at step S11 whether or not the internaltemperature Tr of the refrigerating compartment 24 sensed by therefrigerating compartment temperature sensing unit 112 is higher thanthe desired temperature Trs (for example, about 8° C.) stored in thecontrol unit 120. When the internal temperature Tr of the refrigeratingcompartment 24 is higher than the desired temperature Trs (namely, ifYES), the procedure proceeds to step S12 because the refrigeratingcompartment 24 has been abruptly increased in temperature. At step S12,it is determined whether or not the refrigerating compartment 24 hasbeen maintained for a predetermined time (for example, about 30 minutes)in the state that its internal temperature Tr is higher than the desiredtemperature Trs.

Where it is determined at step S12 that the predetermined time has notelapsed yet (namely, if NO), it is determined that the internaltemperature of the refrigerating compartment 24 has been abruptlyincreased due to the number of accumulated door opening times or theaccumulated door open time. In this case, the procedure returns to stepS10. Then, the procedure from step S10 is repeated.

On the other hand, where it is determined at step S12 that thepredetermined time has elapsed (namely, if YES), it is determined thatthe refrigerating compartment 24 is in an abnormal temperature state. Inthis case, the procedure proceeds to step S13. At step S13, the controlunit 120 applies a control signal to both the compressor driving unit150 and the refrigerating compartment fan motor driving unit 162 of fanmotor driving unit 160 in order to cool the refrigerating compartment 24irrespective of the internal temperature Tf of the freezing compartment22.

Based on the control signal, the compressor driving unit 150 andrefrigerating compartment fan motor driving unit 16f drive thecompressor 56 and refrigerating compartment fan motor 42, respectively.Accordingly, the refrigerating compartment fan 44 is rotated.

When the compressor 56 and refrigerating compartment fan motor 42 aredriven, the cold air heat-exchanged with the refrigerant at therefrigerating compartment evaporator 40 is introduced in therefrigerating compartment 24 through the cold air discharge port 46a bythe rotating force of the refrigerating compartment fan 44.

Thereafter, the procedure proceeds to step S14 to count the drive timeCr of the refrigerating compartment fan 44 by a timer included in thecontrol unit 120.

In order to check the drive time Cr of the refrigerating compartment fan44, it is then determined at step S15 whether or not the drive time Crcounted by the timer is more than a predetermined drive time Cs (forexample, about 40 minutes) stored in the control unit 120.

Where it is determined at step S15 that the predetermined drive time Cshas not elapsed yet (namely, if NO), the procedure returns to step S14.The procedure from the step S14 is then repeated while continuouslysensing the internal temperature Tr of the refrigerating compartment 24.Where it is determined at step S15 that the predetermined drive time Cshas elapsed (namely, YES), the procedure proceeds to step S16 in orderto clear the counted drive time Cr of the refrigerating compartment fan44.

When the refrigerating compartment 24 is still maintained in the statethat its internal temperature Tr is higher than the desired temperatureTrs after being cooled by the continued driving (for about 40 minutes)of the refrigerating compartment fan 44, the procedure proceeds to stepS17 to determine whether or not the increase in the internal temperature(namely, the abnormal temperature state) of the refrigeratingcompartment 24 resulted from a degradation in the heat exchangingability of the refrigerating compartment evaporator 40 caused by frostformed on the evaporator 40. For this determination, it is determinedwhether or not the total drive time Crt of the refrigerating compartmentfan 44 is more than a predetermined total drive time corresponding tothe drive time (for example, 6 hours) of the compressor 56 causing therefrigerating compartment fan 40 to be frosted.

Where it is determined at step S17 that the total drive time Crt is lessthan 6 hours (namely, if NO), it is determined that the abnormaltemperature state of the refrigerating compartment 24 did not resultfrom the formation of frost on the refrigerating compartment evaporator40. In this case, the procedure proceeds to step S10. The procedure fromstep S10 is then repeatedly executed.

On the other hand, where the total drive time Crt is determined at stepS17 as being more than 6 hours (namely, if YES), it is determined thatthe abnormal temperature state of the refrigerating compartment 24resulted from the formation of frost on the refrigerating compartmentevaporator 40. In this case, the procedure proceeds to step S18 of FIG.6C. At step S18, the control until 120 applies a control signal forstopping the cooling operation for the refrigerating compartment 24 toboth the compressor driving unit 150 and the refrigerating compartmentfan motor driving unit 162 of fan motor driving unit 160.

Based on the control signal from the control unit 120, the compressordriving unit 150 and refrigerating compartment fan motor driving unit162 stop the compressor 56 and refrigerating compartment fan motor 42,respectively. As a result, the refrigerating compartment fan 44 is,stopped to prevent the refrigerating compartment 24 from being in anover-cooling state.

At step S19, the control unit 120 then applies a control signal to therefrigerating compartment heater driving unit 132 of the heater drivingunit 130 in order to execute the defrosting operation for removing frostformed on the refrigerating compartment evaporator 40.

Based on the control signal from the control unit 120, the refrigeratingcompartment heater driving unit 132 drives the refrigerating compartmentevaporator's heater 47. Accordingly, the frost formed on therefrigerating compartment evaporator 40 is removed.

While the refrigerating compartment evaporator's heater 47 is generatingheat, the temperature of the refrigerant passing through therefrigerating compartment evaporator 40 is sensed by the refrigeratingcompartment conduit temperature sensing unit 142 of the conduittemperature sensing unit 140. The resultant data from the refrigeratingcompartment conduit temperature sensing unit 142 is then sent to thecontrol unit 120. This procedure is executed at step S20.

At step S21, the control unit 120 then determines whether or not theconduit temperature P2 of the refrigerating compartment evaporator 40sensed by the refrigerating compartment conduit temperature sensing unit142 is higher than a predetermined temperature Prs (namely, a defrostingending temperature capable of completely removing frost formed on therefrigerating compartment evaporator 40) stored in the control unit 120.When the conduit temperature P2 of the refrigerating compartmentevaporator 40 is lower than the predetermined temperature Prs (namely,if NO), it is determined that the frost on the refrigerating compartmentevaporator 40 has been incompletely removed. In this case, the procedurereturns to step S19. The procedure from step S19 is repeatedly executed.

On the other hand, when the conduit temperature P2 of the refrigeratingcompartment evaporator 40 is determined at step S21 as being higher thanthe predetermined temperature Prs (namely, if YES), it is determinedthat the frost on the refrigerating compartment evaporator 40 has beencompletely removed. In this case, the procedure proceeds to step S26. Atstep S26, the control unit 120 sends a control signal to therefrigerating compartment heater driving unit 132 of the heater drivingunit 130 in order to stop the generation of heat from the refrigeratingcompartment evaporator's heater 47.

Based on the control signal from the control unit 120, the refrigeratingcompartment heater driving unit 132 stops the driving of therefrigerating compartment evaporator's heater 471 thereby stopping thedefrosting operation of the refrigerating compartment evaporator 40.

Thereafter, it is determined at step S23 whether or not a predeterminedpause time (namely, a predetermined delay time (for example, about 10minutes) for protecting the compressor 56) has elapsed after thedefrosting operation for the refrigerating compartment 24. Where thepredetermined pause time has not elapsed yet (namely, if NO), theprocedure returns to step S27. The procedure from step S27 is repeateduntil the predetermined pause time elapses.

Where the predetermined pause time has elapsed (namely, if YES), thecompressor 56 is driven to supply cold air to the refrigeratingcompartment 24. In this case, the compressor 56 is not damaged becauseit paused sufficiently.

On the other hand, when the internal temperature Tr of the refrigeratingcompartment 24 is determined at step S11 as being Lower than the desiredtemperature Trs (namely, if NO), the procedure proceeds to step S24. Atstep 24, the drive time Cr of the refrigerating compartment fan 44counted by the timer included in the control unit 120 is cleared.Thereafter, the operation of the refrigerator is completed.

Hereinafter, a method for controlling the defrosting operation of therefrigerator in accordance with a second embodiment of the presentinvention will be described.

FIGS. 7A to 7C are flow charts respectively illustrating the sequence ofthe procedure for controlling the defrosting operation of therefrigerator in accordance with the second embodiment of the presentinvention.

Once the refrigerator is powered, the DC power supply unit 90 converts asource voltage received from a commercial AC power source at the ACpower input stage (not shown) into a DC voltage with a voltage levelrequired to drive various units of the refrigerator. The DC voltage fromthe DC power supply unit 90 is then applied to the control unit 120 aswell as various driving circuits.

At step S31 of FIG. 7A, the control unit 120 initializes therefrigerator in response to the DC voltage received from the DC powersupply unit 90 in order to operate the refrigerator. At step S32, it isdetermined whether or not the compressor 56 is being driven. Thisdetermination is made when the internal temperature of the freezingcompartment 22 or refrigerating compartment 24 is higher than a desiredtemperature set by the user using the temperature setting unit 100.

When it is determined at step S32 that the compressor 56 is being driven(namely, if YES), the procedure proceeds to step S33. At step S33, it isdetermined that the refrigerating compartment fan 44 is being driven.Where the refrigerating compartment fan 44 is being driven (namely, ifYES), step S34 is executed to count the drive time Cr of therefrigerating compartment fan 44 by the timer included in the controlunit 120.

Subsequently, it is determined at step S35 whether or not the freezingcompartment fan 30 is being driven. When the freezing compartment fan 30is not driven (namely, if NO), the procedure returns to step S33. Theprocedure from step S33 is then repeatedly executed.

Where it is determined at step S35 that the freezing compartment fan 30is being driven (namely, if YES), step S36 is executed. At step S36, thedrive time Cf of the freezing compartment fan 30 is counted by a timerincluded in the control unit 120. Thereafter, the procedure proceeds tostep S37 to determine whether or not the operation mode of therefrigerator corresponds to the overload operation mode.

When the operation mode of the refrigerator is determined at step S37 ascorresponding to the overload operation mode (namely, if YES), theprocedure proceeds to step S38. At step S38, the drive time Cf of thefreezing compartment fan 30 counted at step S36 is set as the drive timeCm of the compressor 56 for the freezing operation.

On the other hand, where the operation mode of the refrigerator isdetermined at step S37 as not corresponding to the overload operationmode (namely, if NO), the procedure proceeds to step S39. At step S39,the drive time Cr of the refrigerating compartment fan 44 counted atstep S34 is set as the drive time Cn of the compressor 56 for therefrigerating operation.

Thereafter, the total drive time Ct of the compressor 56 is calculatedat step S40 by adding the drive time Cn derived at step S39 to the drivetime Cm derived at step S38. It is then determined at step S41 of FIG.7B whether or not the total drive time Ct of the compressor 56 is morethan a predetermined time C1 (the total drive time (for example, 10hours) of the compressor 56 causing the freezing compartment evaporator26 to be frosted) stored in the control unit 120.

Where the total drive time Ct of the compressor 56 is determined at stepS41 as being more than the predetermined time C1 (namely, if YES), it isdetermined that the freezing compartment evaporator 26 should bedefrosted (that is, it is under a defrost requiring condition). Upondefrosting the freezing compartment evaporator 26, the refrigeratingcompartment evaporator 40 is simultaneously defrosted. To this end, itis necessary to check the defrost requiring condition of therefrigerating compartment evaporator 40. Accordingly, it is determinedat step S42 whether or not the drive time Cr of the refrigeratingcompartment fan 44 counted by the timer included in the control unit 120is more than a predetermined time C2 (namely, the total drive time (forexample, about 9 hours) of the compressor 56 causing the refrigeratingcompartment fan 40 to be frosted.

When the counted drive time Cr of the refrigerating compartment fan 44is determined at step S42 as being more than the predetermined time C2(namely, if YES), step S43 is executed to defrost both the freezing andrefrigerating compartment evaporators 26 and 40. As step S43, thecontrol unit 120 sends a control signal to the compressor driving unit150 and the freezing and refrigerating compartment fan motor drivingunits 161 and 162 of the fan motor driving unit 160 in order to stop thecooling operation for the freezing and refrigerating compartments 22 and24.

Based on the control signal from the control unit 120, the compressordriving unit 150 and the freezing and refrigerating compartment fanmotor driving units 161 and 162 stop the compressor 56 and the freezingand refrigerating compartment fan motors 28 and 42, respectively. As aresult, the freezing and refrigerating compartment fans 30 and 44 arestopped, thereby stopping the cooling operation for the freezing andrefrigerating compartments 22 and 24.

At step S44, the control unit 120 then applies a control signal to boththe freezing and refrigerating compartment heater driving units 131 and132 of the heater driving unit 130 in order to execute the defrostingoperation for removing frost formed on the freezing and refrigeratingcompartment evaporators 26 and 40.

Based on the control signal from the control unit 120, the freezing andrefrigerating compartment heater driving units 131 and 132 drive thefreezing and refrigerating compartment evaporator's heaters 33 and 47,respectively. Accordingly, the frost formed on the freezing andrefrigerating compartment evaporators 26 and 40 is removed by heatgenerated at the freezing and refrigerating compartment evaporator'sheaters 33 and 47.

At step S45, the conduit temperature P1 of the freezing compartmentevaporator 26 being varied while the freezing compartment evaporator'sheater 33 is generating heat, namely, the temperature of the refrigerantpassing through the freezing compartment evaporator 26 is sensed by thefreezing compartment conduit temperature sensing unit 141 of the conduittemperature sensing unit 140.

At step S46, the control unit 120 then determines whether or not theconduit temperature P1 of the freezing compartment evaporator 26 sensedby the freezing compartment conduit temperature sensing unit 141 ishigher than a predetermined temperature Pfs (namely, a defrosting endingtemperature capable of completely removing frost formed on the freezingcompartment evaporator 26) stored in the control unit 120. When theconduit temperature P1 of the freezing compartment evaporator 26 islower than the predetermined temperature Pfs (namely, if NO), it isdetermined that the frost on the freezing compartment evaporator 40 hasbeen incompletely removed. In this case, the procedure returns to stepS44. The procedure from step S44 is repeatedly executed.

On the other hand, when the conduit temperature P1 of the freezingcompartment evaporator 26 is determined at step S46 as being higher thanthe predetermined temperature Pfs (namely, if YES), it is determinedthat the frost on the freezing compartment evaporator 26 has beencompletely removed. In this case, the procedure proceeds to step S47. Atstep S47, the control unit 120 sends a control signal to the freezingcompartment heater driving unit 131 of the heater driving unit 130 inorder to stop the generation of heat from the freezing compartmentevaporator's heater 33.

Based on the control signal from the control unit 120, the freezingcompartment heater driving unit 131 stops the driving of the freezingcompartment evaporator's heater 33, thereby stopping the defrostingoperation for the freezing compartment 22.

Thereafter, the refrigerating compartment conduit temperature sensingunit 142 of the conduit temperature sensing unit 140 senses, at stepS48, the conduit temperature P2 of the refrigerating compartmentevaporator 40, namely, the temperature of the refrigerant passingthrough the refrigerating compartment evaporator 40 while therefrigerating compartment evaporator's heater 47 is generating heat. Theresultant data from the refrigerating compartment conduit temperaturesensing unit 142 is sent to the control unit 120.

At step S49, the control unit 120 then determines whether or not theconduit temperature P2 of the refrigerating compartment evaporator 40sensed by the refrigerating compartment conduit temperature sensing unit142 is higher than a predetermined temperature Prs (namely, a defrostingending temperature capable of completely removing frost formed on therefrigerating compartment evaporator 40) stored in the control unit 120.When the conduit temperature P2 of the refrigerating compartmentevaporator 40 is lower than the predetermined temperature Prs (namely,if NO), it is determined that the frost on the refrigerating compartmentevaporator 40 has been incompletely removed. In this case, the procedurereturns to step S44. The procedure from step S44 is repeatedly executed.

On the other hand, when the conduit temperature P2 of the refrigeratingcompartment evaporator 40 is determined at step S49 as being higher thanthe predetermined temperature Prs (namely, if YES), it is determinedthat the frost on the refrigerating compartment evaporator 40 has beencompletely removed. In this case, the procedure proceeds to step S50 ofFIG. 7C. At step S50, the control unit 120 sends a control signal to therefrigerating compartment heater driving unit 132 of the heater drivingunit 130 in order to stop the generation of heat from the refrigeratingcompartment evaporator's heater 47.

Based on the control signal from the control unit 120, the refrigeratingcompartment heater driving unit 132 stops the generation of heat fromthe refrigerating compartment evaporator's heater 47, thereby stoppingthe defrosting operation for the refrigerating compartment 24.

Thereafter, it is determined at step S51 whether or not a predeterminedpause time (namely, a predetermined delay time (for example, about 10minutes) for protecting the compressor 56) has elapsed after thedefrosting operation for the freezing and refrigerating compartments 22and 24. Where the predetermined pause time has not elapsed yet (namely,if NO), the procedure returns to step S51. The procedure from step S51is repeated until the predetermined pause time elapses.

Where the predetermined pause time has elapsed (namely, if YES), thecompressor 56 is driven to execute the freezing operation for thefreezing compartment 22 or the refrigerating operation for therefrigerating compartment 24. In this case, the compressor 56 is notdamaged because it paused sufficiently.

On the other hand, when it is determined at step S32 that the compressor56 is not driven (namely, if YES), it is determined that neither thefreezing compartment 22 nor the refrigerating compartment 24 is underthe defrost requiring condition. In this case, the control unit 120 doesnot execute any control for the defrosting operation of therefrigerator. Where the total drive time Ct of the compressor 56 isdetermined at step S41 as being less than the predetermined time C1(namely, if NO), neither the freezing compartment 22 nor therefrigerating compartment 24 is under the defrost requiring condition.Accordingly, the control unit 120 does not execute any control for thedefrosting operation for the refrigerator.

Where the drive time Cr of the refrigerating compartment fan 44 isdetermined at step S42 as being less than the predetermined time C2(namely, if NO), it is determined that the freezing compartment 22requires the defrosting operation whereas the refrigerating compartment22 does not require the defrosting operation. In this case, theprocedure proceeds to step S53. At step 53, the control unit 120 appliesa control signal for stopping the cooling operation for the freezing andrefrigerating compartments 22 and 24 to the compressor driving unit 150and the freezing and refrigerating compartment fan motor driving units161 and 162 of the fan motor driving unit 160.

Based on the control signal from the control unit 120, the compressordriving unit 150 and the freezing and refrigerating compartment fanmotor driving units 161 and 162 stop the compressor 56 and the freezingand refrigerating compartment fan motors 28 and 42, respectively. As aresult, the freezing and refrigerating compartment fans 30 and 44 arestopped, thereby stopping the cooling operation for the freezing andrefrigerating compartments 22 and 24.

At step S54, the control unit 120 then applies a control signal to thefreezing compartment heater driving unit 131 of the heater driving unit130 in order to execute the defrosting operation for removing frostformed on the freezing compartment evaporator 26.

Based on the control signal from the control unit 120, the freezingcompartment heater driving unit 131 drives the freezing compartmentevaporator's heater 33. Accordingly, the frost formed on the freezingcompartment evaporator 26 is removed by heat generated at the freezingcompartment evaporator's heater 33.

At step S55, the conduit temperature P1 of the freezing compartmentevaporator 26 being varied while the freezing compartment evaporator'sheater 33 is generating heat is sensed by the freezing compartmentconduit temperature sensing unit 141 of the conduit temperature sensingunit 140. The resultant data from the freezing compartment conduittemperature sensing unit 141 is sent to the control unit 120. At stepS56, the control unit 120 then determines whether or not the conduittemperature P1 of the freezing compartment evaporator 26 sensed by thefreezing compartment conduit temperature sensing unit 141 is higher thana predetermined temperature Pfs stored in the control unit 120.

When the conduit temperature P1 of the freezing compartment evaporator26 is determined at step S56 as being lower than the predeterminedtemperature Pfs (namely, if NO), it is determined that the frost on thefreezing compartment evaporator 40 has been incompletely removed. Inthis case, the procedure returns to step S54. The procedure from stepS54 is repeatedly executed.

On the other hand, where the conduit temperature P1 of the freezingcompartment evaporator 26 is determined at step S56 as being higher thanthe predetermined temperature Pfs (namely, if YES), it is determinedthat the frost on the freezing compartment evaporator 26 has beencompletely removed. In this case, the procedure proceeds to step S57. Atstep S57, the control unit 120 sends a control signal to the freezingcompartment heater driving unit 131 of the heater driving unit 130 inorder to stop the driving of the freezing compartment evaporator'sheater 33.

Based on the control signal from the control unit 120, the freezingcompartment heater driving unit 131 stops the driving of the freezingcompartment evaporator's heater 33, thereby causing the heater 33 togenerate heat no longer. As a result, the defrosting operation for thefreezing compartment 22 is stopped. Thereafter, it is determined at stepS51 whether or not the predetermined pause time has elapsed after thedefrosting operation for the freezing compartment 22. The procedure fromstep S51 is then repeated.

Now, a method for controlling the defrosting operation of therefrigerator in accordance with a third embodiment of the presentinvention will be described.

FIGS. 8A and 8B are flow charts respectively illustrating the sequenceof the procedure for controlling the defrosting operation of therefrigerator in accordance with the third embodiment of the presentinvention.

Once the refrigerator is powered, the DC power supply unit 90 converts asource voltage received from a commercial AC power source at the ACpower input stage (not shown) into a DC voltage with a voltage levelrequired to drive various units of the refrigerator. The DC voltage fromthe DC power supply unit 90 is then applied to the control unit 120 aswell as various driving circuits.

At step S61 of FIG. 8A, the control unit 120 initializes therefrigerator in response to the DC voltage received from the DC powersupply unit 90 in order to operate the refrigerator. At step S62, thedesired internal temperatures Tfs and Trs of the freezing andrefrigerating compartments 22 and 24 are set using the freezing andrefrigerating compartment temperature setting units.101 and 102 of thetemperature setting unit 100.

The procedure then proceeds to step S63. At step S63, it is determinedwhether or not the internal temperature Tf of the freezing compartment22 sensed by the freezing compartment temperature sensing unit 111 ishigher than the desired temperature Tfs set by the freezing compartmenttemperature setting unit 101.

Where the internal temperature Tf of the freezing compartment 22 isdetermined at step S63 as being lower than the desired temperature Tfs(namely, if NO), the procedure returns to step S63. The procedure fromstep S63 is then repeated while continuously sensing the internaltemperature Tf of the freezing compartment 22 until the temperature Tfis higher than the desired temperature Tfs.

On the other hand, when the current internal temperature Tf of thefreezing compartment 22 is determined at step S63 as being higher thanthe desired temperature Tfs (namely, if YES), the procedure proceeds tostep S64. At step S64, the control unit 120 applies a control signal fordriving the compressor 56 to the compressor driving unit 150. Based onthe control signal, the compressor 56 is driven.

Subsequently, it is determined at step S65 whether the current internaltemperature Tr of the refrigerating compartment 24 is higher than thedesired temperature Trs.

Where the internal temperature Tr of the refrigerating compartment 24 ishigher than the desired temperature Trs, the procedure proceeds to stepS66. At step S66, the control unit 120 applies a control signal to therefrigerating compartment fan motor driving unit 162 of the fan motordriving unit 160 in order to first cool the refrigerating compartment24. Based on the control signal from the control unit 120, therefrigerating compartment fan motor 42 is driven, thereby rotating therefrigerating compartment fan 44 coupled to the rotating shaft of therefrigerating compartment fan motor 42. As a result, the refrigeratingcompartment 24 is cooled.

Thereafter, the procedure proceeds to step S67 to count the drive timeCr of the refrigerating compartment fan 44 by the timer included in thecontrol unit 120.

Where the compressor 56 and refrigerating compartment fan motor 42 aredriven while the freezing compartment fan motor 28 is being stopped,only the refrigerating compartment evaporator 40 can carry out a heatexchange between refrigerant and ambient air. That is, refrigerantcompressed to a gaseous phase of high temperature and pressure isdischarged out of the compressor 56 toward the assistant condenser 60.While passing through the assistant condenser 60, the refrigerantevaporates water collected in the evaporating dish 54. The refrigerantis then introduced in the main condenser 58. While passing through themain condenser 58, the refrigerant carries out a heat exchange withambient air in accordance with the natural or forced convectionphenomenon, so that it is cooled to have a liquid phase under lowtemperature and high pressure. That is, the refrigerant is liquefied.

The liquid-phase refrigerant of low temperature and high pressure, whichhas been liquefied in the main condenser 58, then passes through thecapillary tube 57. By the capillary tube 57, the refrigerant is changedto that of low temperature and pressure so that it can be easilyevaporated. The refrigerant emerging from the capillary tube 57 is thenintroduced in the freezing and refrigerating compartment evaporators 26and 40.

While passing through the freezing and refrigerating compartmentevaporators 26 and 40, each of which is constituted by a plurality ofpipes, the refrigerant of low temperature and pressure carries out aheat exchange with air being blown into the freezing and refrigeratingcompartments 22 and 24. By this heat exchange, the refrigerant isvaporized while cooling the air. The resultant gaseous refrigerant flowsof low temperature and pressure respectively emerging from the freezingand refrigerating compartment evaporators 26 and 40 are then introducedin the compressor 56. Thus, the refrigerant circulates the refrigeratingcycle of FIG. 4 repeatedly.

In the above case, however, there is no flow of air being blown towardthe freezing compartment 22 because the freezing compartment fan 30 isnot driven. Accordingly, the heat exchange is carried out only at therefrigerating compartment evaporator 40.

The cold air heat-exchanged with the refrigerant by the refrigeratingcompartment evaporator 40 is blown by the rotating force of therefrigerating compartment fan 44 and guided by the refrigeratingcompartment duct member 46 so that it is discharged into therefrigerating compartment 24 through the cold air discharge port 46a. Asa result, the refrigerating compartment 24 is cooled.

While the compressor 56 and refrigerating compartment fan 44 are beingdriven, the refrigerating compartment temperature sensing unit 113senses the current internal temperature Tr of the refrigeratingcompartment 24 and sends the resultant data to the control unit 120.

At step S67, the drive time Cr of the refrigerating compartment fan 44is counted by the timer included in the control unit 120. Thereafter,the procedure proceeds to step S68 to determine whether or not theoperation mode of the refrigerator corresponds to the overload operationmode, that is, whether the number of times the refrigerating compartmentdoor has been opened is more than a predetermined value. When theoperation mode of the refrigerator is determined at step S68 ascorresponding to the overload operation mode (namely, if YES), theprocedure proceeds to step S69. At step S69, the drive time Cr of therefrigerating compartment fan 44 counted at step S67 is multiplied by 2.The resultant value is set as the drive time Cm of the compressor 56.For the drive time Cm, the refrigerator is operated.

On the other hand, where the operation mode of the refrigerator isdetermined at step S68 as not corresponding to the overload operationmode (namely, if NO), the procedure proceeds to step S70. At step S70,the drive time Cr of the refrigerating compartment fan 44 counted atstep S67 is set as the drive time Cm of the compressor 56.

Thereafter, it is determined at step S71 whether or not the drive timeCm of the compressor 56 is more than a predetermined time C1 (the drivetime (for example, 10 hours) of the compressor 56 causing therefrigerating compartment evaporator 40 to be frosted) stored in thecontrol unit 120.

Where the drive time Cm of the compressor 56 is determined at step S71as being less than the predetermined time C1 (namely, if NO), step S72is executed to determine whether or not the current internal temperatureTr of the refrigerating compartment 24 sensed by the refrigeratingcompartment temperature sensing unit 113 is lower than the desiredtemperature Trs set by the user.

When the current internal temperature Tr of the refrigeratingcompartment 24 is determined at step S72 as being higher than thedesired temperature Trs, the procedure proceeds to step S66. Theprocedure from step S66 is repeated to continuously cool therefrigerating compartment 24.

On the other hand, when the current internal temperature Tr of therefrigerating compartment 24 is determined at step S72 as being lowerthan the desired temperature Trs, the control unit 120 applies, at stepS73, a control signal for stopping the cooling operation for therefrigerating compartment 24 to the refrigerating compartment fan motordriving unit 162 of the fan motor driving unit 160. Based on the controlsignal, the refrigerating compartment fan motor 42 is stopped, therebystopping the cooling operation for the refrigerating compartment 24.

Thereafter, the procedure proceeds to step S74 of FIG. 8B to cool thefreezing compartment 22. At step S74, the control unit 120 applies acontrol signal to the freezing compartment fan motor driving unit 161 ofthe fan motor driving unit 160. Based on the control signal from thecontrol unit 120, the freezing compartment fan motor 28 is driven,thereby rotating the freezing compartment fan 30 coupled to the rotatingshaft of the freezing compartment fan motor 28. At step S75, the drivetime Cf of the freezing compartment fan 30 is then counted by the timerincluded in the control unit 120.

Where the freezing compartment fan motor 28 is driven while therefrigerating compartment fan motor 42 is being stopped, only thefreezing compartment evaporator 26 can carry out a heat exchange betweenrefrigerant and ambient air. That is, refrigerant compressed to agaseous phase of high temperature and pressure is discharged out of thecompressor 56 toward the assistant condenser 60. While passing throughthe assistant condenser 60, the refrigerant evaporates water containedin the evaporating dish 54. The refrigerant is then introduced in themain condenser 58. While passing through the main condenser 58, therefrigerant carries out a heat exchange with ambient air in accordancewith the natural or forced convection phenomenon, so that it is cooledto have a liquid phase under low temperature and high pressure. That is,the refrigerant is liquefied.

The liquid-phase refrigerant of low temperature and high pressure, whichhas been liquefied in the main condenser 58, then passes through thecapillary tube 57. By the capillary tube 57, the refrigerant is changedto that of low temperature and pressure so that it can be easilyevaporated. The refrigerant emerging from the capillary tube 57 is thenintroduced in the freezing and refrigerating compartment evaporators 26and 40.

While passing through the freezing and refrigerating compartmentevaporators 26 and 40, each of which is constituted by a plurality ofpipes, the refrigerant of low temperature and pressure carries out aheat exchange with air being blown into the freezing and refrigeratingcompartments 22 and 24. By this heat exchange, the refrigerant isvaporized while cooling the air. The resultant gaseous refrigerant flowsof low temperature and pressure respectively emerging from the freezingand refrigerating compartment evaporators 26 and 40 are then introducedin the compressor 56. Thus, the refrigerant circulates the refrigeratingcycle of FIG. 4 repeatedly.

In the above case, however, there is no flow of air being blown towardthe refrigerating compartment 24 because the refrigerating compartmentfan 44 is not driven. Accordingly, the heat exchange is carried out onlyat the freezing compartment evaporator 26.

The cold air heat-exchanged with the refrigerant by the freezingcompartment evaporator 26 is blown by the rotating force of the freezingcompartment fan 30 and guided by the freezing compartment duct member 32so that it is discharged into the freezing compartment 22 through thecold air discharge port 32a. As a result, the freezing compartment 22 iscooled.

Where the freezing compartment fan 30 is driven along with thecompressor 56, thereby carrying out the cooling operation for thefreezing compartment 22 for a certain period of time, the internaltemperature Tf of the freezing compartment 22 is gradually lowered. Thisinternal temperature Tf of the freezing compartment 22 is sensed by thefreezing compartment temperature sensing unit 111 of the temperaturesensing unit 110. The resultant data from the freezing compartmenttemperature sensing unit 111 is then applied to the control unit 120.

At step S76, it is then determined whether or not the drive time Cf ofthe freezing compartment fan 30 counted by the timer included in thecontrol unit 120 is more than the predetermined time C1 stored in thecontrol unit 120.

When the counted drive time Cf of the freezing compartment fan 30 isdetermined at step S76 as being more than the predetermined time C1(namely, if YES), step S77 is executed to defrost both the freezing andrefrigerating compartment evaporators 26 and 40. As step S77, thecontrol unit 120 sends a control signal to the compressor driving unit150 and the freezing and refrigerating compartment fan motor drivingunits 161 and 162 of the fan motor driving unit 160 in order to stop thecooling operation for the freezing and refrigerating compartments 22 and24.

Based on the control signal from the control unit 120, the compressordriving unit 150 and the freezing and refrigerating compartment fanmotor driving units 161 and 162 stop the compressor 56 and the freezingand refrigerating compartment fan motors 28 and 42, respectively. As aresult, the freezing and refrigerating compartment fan motors 28 and 42are stopped, thereby stopping the cooling operation for the freezing andrefrigerating compartments 22 and 24.

At step S78, the control unit 120 then applies a control signal to boththe freezing and refrigerating compartment heater driving Units 131 and132 of the heater driving unit 130 in order to execute the defrostingoperation for removing frost formed on the freezing and refrigeratingcompartment evaporators 26 and 40. Based on the control signal from thecontrol unit 120, the freezing and refrigerating compartment heaterdriving units 131 and 132 drive the freezing and refrigeratingcompartment evaporator's heaters 33 and 47, respectively. Accordingly,the frost formed on the freezing and refrigerating compartmentevaporators 26 and 40 is removed by heat generated at the freezing andrefrigerating compartment evaporator's heaters 33 and 47.

At step S79, the conduit temperature P1 of the freezing compartmentevaporator 26, that is, the temperature P1 of the refrigerant passingthrough the freezing compartment evaporator 26 is sensed by the freezingcompartment conduit temperature sensing unit 141 of the conduittemperature sensing unit 140. The resultant data is sent to the controlunit 120. At step S80, the control unit 120 then determines whether ornot the conduit temperature P1 of the freezing compartment evaporator 26is higher than a predetermined temperature Pfs (namely, a defrostingending temperature capable of completely removing frost formed on thefreezing compartment evaporator 26) stored in the control unit 120. Whenthe conduit temperature P1 of the freezing compartment evaporator 26 islower than the predetermined temperature Pfs (namely, if NO), it isdetermined that the frost on the freezing compartment evaporator 40 hasbeen incompletely removed. In this case, the procedure returns to stepS78. The procedure from step S78 is repeated until the conduittemperature P1 of the freezing compartment evaporator 26 reaches thepredetermined temperature Pfs.

On the other hand, when the conduit temperature P1 of the freezingcompartment evaporator 26 is determined at step S80 as being higher thanthe predetermined temperature Pfs (namely, if YES), it is determinedthat the frost on the freezing compartment evaporator 26 has beencompletely removed. In this case, the procedure proceeds to step S81. Atstep S81, the control unit 120 sends a control signal to the freezingcompartment heater driving unit 131 of the heater driving unit 130 inorder to stop the generation of heat from the freezing compartmentevaporator's heater 33. Based on the control signal from the controlunit 120, the freezing compartment heater driving unit 131 stops thedriving of the freezing compartment evaporator's heater 33, therebystopping the defrosting operation for the freezing compartment 22.

Thereafter, the refrigerating compartment conduit temperature sensingunit 142 of the conduit temperature sensing unit 140 senses, at stepS82, the conduit temperature P2 of the refrigerating compartmentevaporator 40, namely, the temperature of the refrigerant passingthrough the refrigerating compartment evaporator 40. The resultant datais sent to the control unit 120. At step S83, the control unit 120 thendetermines whether or not the conduit temperature P2 of therefrigerating compartment evaporator 40 is higher than a predeterminedtemperature Prs (namely, a defrosting ending temperature capable ofcompletely removing frost formed on the refrigerating compartmentevaporator 40) stored in the control unit 120. When the conduittemperature P2 of the refrigerating compartment evaporator 40 is lowerthan the predetermined temperature Prs (namely, if NO), it is determinedthat the frost on the refrigerating compartment evaporator 40 has beenincompletely removed. In this case, the procedure returns to step S78.The procedure from step S78 is repeatedly executed until the conduittemperature P2 of the refrigerating compartment evaporator 40 reachesthe predetermined temperature Prs.

On the other hand, when the conduit temperature P2 of the refrigeratingcompartment evaporator 40 is determined at step S49 as being higher thanthe predetermined temperature Prs (namely, if YES), it is determinedthat the frost on the refrigerating compartment evaporator 40 has beencompletely removed. In this case, the procedure proceeds to step S84. Atstep S84, the control unit 120 sends a control signal to therefrigerating compartment heater driving unit 132 of the heater drivingunit 130 in order to stop the generation of heat from the refrigeratingcompartment evaporator's heater 47. Based on the control signal from thecontrol unit 120, the refrigerating compartment heater driving unit 132stops the generation of heat from the refrigerating compartmentevaporator's heater 47, thereby stopping the defrosting operation forthe refrigerating compartment 24.

Thereafter, it is determined at step S85 whether or not a predeterminedpause time (namely, a predetermined delay time (for example, about 10minutes) for protecting the compressor 56) has elapsed after thedefrosting operation for the freezing and refrigerating compartments 22and 24. Where the predetermined pause time has not elapsed yet (namely,if NO), the procedure from step S85 is repeated until the predeterminedpause time elapses.

Where the predetermined pause time has elapsed (namely, if YES), thecompressor 56 can be driven again. In this case, the compressor 56 isnot damaged because it paused sufficiently. Accordingly, the controlunit 120 stops the defrosting operation of the refrigerator and thenclears, at step S86, the counted drive times Cf and Cr of the freezingand refrigerating compartment fans 30 and 44. Thus, the defrostingoperation is completed.

On the other hand, when it is determined at step S76 that the drive timeCf of the freezing compartment fan 30 is less than the predeterminedtime C1 (namely, if NO), neither the freezing compartment 22 nor therefrigerating compartment 24 is under the defrost requiring condition.In this case, the procedure proceeds to step S87. At step S87, it isdetermined whether or not the current internal temperature Tf of thefreezing compartment 22 sensed by the freezing compartment temperaturesensing unit 111 of the temperature sensing unit 110 is lower than thepredetermined temperature Tfs stored in the control unit 120. When theinternal temperature Tf of the freezing compartment 22 is higher thanthe predetermined temperature Tfs (namely, if NO), the procedure returnsto step S74 to continuously cool the freezing compartment 22. Theprocedure from step S74 is repeatedly executed.

When the internal temperature Tf of the freezing compartment 22 isdetermined at step S87 as being lower than the predetermined temperatureTfs (namely, if YES), the procedure proceeds to step S88. At step S88,the control unit 120 applies a control signal for stopping the coolingoperation for the freezing compartment 22 to the compressor driving unit150 and the freezing compartment fan motor driving unit 161 of the fanmotor driving unit 160.

Based on the control signal from the control unit 120, the compressordriving unit 150 and freezing compartment fan motor driving unit 161stop the compressor 56 and freezing compartment fan motor 28,respectively. As a result, the cooling operation for the freezingcompartment 22 is completed. Thereafter, the procedure returns to stepS63. The procedure from S63 is then repeated.

Hereinafter, a method for controlling the defrosting operation of therefrigerator in accordance with a fourth embodiment of the presentinvention will be described.

FIGS. 9A and 9B are flow charts respectively illustrating the sequenceof the procedure for controlling the defrosting operation of therefrigerator in accordance with the fourth embodiment of the presentinvention.

Once the refrigerator is powered, the DC power supply unit 90 converts asource voltage received from a commercial AC power source at the ACpower input stage (not shown) into a DC voltage with a voltage levelrequired to drive various units of the refrigerator. The DC voltage fromthe DC power supply unit 90 is then applied to the control unit 120 aswell as various driving circuits.

At step S91 of FIG. 9A, the control unit 120 initializes therefrigerator in response to the DC voltage received from the DC powersupply unit 90 in order to operate the refrigerator. At step S92, thedesired internal temperatures Tfs and Trs of the freezing andrefrigerating compartments 22 and 24 are set by manipulating thefreezing and refrigerating compartment temperature setting units 101 and102 of the temperature setting unit 100. The procedure then proceeds tostep S93 to determine whether or not the rapid refrigerating switch isin its ON state. When the rapid refrigerating switch is determined atstep S93 as not being in its ON state (namely, if NO), the control unit102 executes the procedure from the step S93 while controlling therefrigerator to standby for its rapid refrigerating operation.

When the rapid refrigerating switch is determined at step S93 as beingin its ON state (namely, if YES), the procedure proceeds to step S94 toexecute the rapid refrigerating operation for the refrigeratingcompartment 24. At step S94, the refrigerating compartment temperaturesensing unit 112 of the temperature sensing unit 110 senses the internaltemperature T0 of the refrigerating compartment 24 at the point of timewhen the rapid refrigerating operation begins. The resultant data issent to the control unit 120. Thereafter, the procedure proceeds to stepS95. At step S95, the control unit 120 applies a control signal forrapidly cooling the refrigerating compartment 24 to both the compressordriving unit 150 and the refrigerating compartment fan motor drivingunit 162 of the fan motor driving unit 160. Based on the control signal,the refrigerating compartment fan motor 42 is driven, thereby rotatingthe refrigerating compartment fan 44 coupled to the rotating shaftthereof.

Where the compressor 56 and refrigerating compartment fan 44 are drivenwhile the freezing compartment fan 30 is being stopped, only therefrigerating compartment evaporator 40 can carry out a heat exchangebetween refrigerant and ambient air. That is, refrigerant compressed toa gaseous phase of high temperature and pressure is discharged out ofthe compressor 56 toward the assistant condenser 60. While passingthrough the assistant condenser 60, the refrigerant evaporates watercollected in the evaporating dish 54. The refrigerant is then introducedin the main condenser 58. While passing through the main condenser 58,the refrigerant carries out a heat exchange with ambient air inaccordance with the natural or forced convection phenomenon, so that itis cooled to have a liquid phase under low temperature and highpressure. That is, the refrigerant is liquefied.

The liquid-phase refrigerant of low temperature and high pressure, whichhas been liquefied in the main condenser 58, then passes through thecapillary tube 57. By the capillary tube 57, the refrigerant is changedto that of low temperature and pressure so that it can be easilyevaporated. The refrigerant emerging from the capillary tube 57 is thenintroduced in the freezing and refrigerating compartment evaporators 26and 40.

While passing through the freezing and refrigerating compartmentevaporators 26 and 40, each of which is constituted by a plurality ofpipes, the refrigerant of low temperature and pressure carries out aheat exchange with air being blown into the freezing and refrigeratingcompartments 22 and 24. By this heat exchange, the refrigerant isvaporized while cooling the air. The resultant gaseous refrigerant flowsof low temperature and pressure respectively emerging from the freezingand refrigerating compartment evaporators 26 and 40 are then introducedin the compressor 56. Thus, the refrigerant circulates the refrigeratingcycle of FIG. 4 repeatedly.

In the above case, however, there is no flow of air being blown towardthe freezing compartment 22 because the freezing compartment fan 30 isnot driven. Accordingly, no heat exchange is carried out at the freezingcompartment evaporator 26. The heat exchange is carried out only at therefrigerating compartment evaporator 40.

The cold air heat-exchanged with the refrigerant by the refrigeratingcompartment evaporator 40 is blown by the rotating force of therefrigerating compartment fan 44 and guided by the refrigeratingcompartment duct member 46 so that it is discharged into therefrigerating compartment 24 through the cold air discharge port 46a.Thus, the rapid refrigerating operation for the refrigeratingcompartment 24 is executed.

The refrigerating compartment temperature sensing unit 112 senses thecurrent internal temperature Tr of the refrigerating compartment 24being varied during the rapid refrigerating operation for therefrigerating compartment 24 carried out by driving the compressor 56and refrigerating compartment fan 44. The resultant data is sent to thecontrol unit 120.

Subsequently, the procedure proceeds to step S96. At this step, thedrive time Cr of the refrigerating compartment fan 44 is counted by thetimer included in the control unit 120. It is then determined at stepS97 whether or not the counted drive time Cr of the refrigeratingcompartment fan 44 is more than a sampling time Δt (a reference time(about 10 minutes) required to determine a variation in the internaltemperature of the refrigerating compartment 24 during the rapidrefrigerating operation).

When the counted drive time Cr of the refrigerating compartment fan 44is determined at step S97 as being more than the sampling time Δt(namely, if YES), the procedure proceeds to step S98. At this step, therefrigerating compartment temperature sensing unit 112 senses theinternal temperature Tr of the refrigerating compartment 24 and sendsthe resultant data to the control unit 120. Thereafter, the procedureproceeds to step S99 to determine whether or not the refrigeratingcompartment 24 should be defrosted, that is, whether or not therefrigerating compartment 24 is under the defrost requiring condition.For this determination, the drive time Cr of the refrigeratingcompartment fan 44 counted during the rapid refrigerating operation andthe drive time of the refrigerating compartment fan 44 counted duringthe normal mode operation are accumulated. it is then determined whetheror not the accumulated drive time is more than a predetermined timecorresponding to the drive time causing the refrigerating compartmentevaporator 40 to be frosted.

Where the refrigerating compartment 24 is determined at step S99 asbeing under the defrost requiring condition (namely, if YES), step S100is executed. At step S100, it is determined whether or not the drivetime Cr of the refrigerating compartment fan 44 counted during the rapidrefrigerating operation is more than a predetermined time (for example,about 20 minutes or above).

The reason for determining whether or not the predetermined time haselapsed is because at least two sampling data are required uponcalculating a temperature drop gradient Ta corresponding the variationin the internal temperature of the refrigerating compartment 24 on thebasis of the internal temperature Tr of the refrigerating compartment 24sensed for each sampling time Δt so that the calculated temperature dropgradient Ta can be accurate.

When it is determined at step S100 that the predetermined time has notelapsed yet (namely, if NO), the procedure returns to step S96. Theprocedure from step S96 is then repeatedly executed. When thepredetermined time has elapsed (namely, if YES), the procedure proceedsto step S101. Since the variation in the internal temperature of therefrigerating compartment 24 can be accurately calculated in this case,the temperature drop gradient Ta corresponding to the variation of therefrigerating compartment's temperature during the rapid refrigeratingoperation till the current time point is calculated at step 101.

Assuming that 50 minutes elapsed from the beginning of the rapidrefrigerating operation, the number of data about sensed internaltemperature is five because the sampling time Δ is about 10 minutes inthe above case.

Accordingly, the temperature drop gradient Ta is calculated by derivingthe absolute value of the difference between the internal temperaturedata T5 at the point of time when 50 minutes elapsed from the beginningof the rapid refrigerating operation and the internal temperature dataT0 at the point of time when the rapid refrigerating operation begins,and then dividing the derived absolute value by the number of samplingtimes, namely, 5, as expressed by the following equation (1):

    Ta=(T5-T0)/5                                               (1)

After calculating the temperature drop gradient Ta as above, theprocedure proceeds to step S102 of FIG. 9B. At step S102, it isdetermined whether or not the temperature drop gradient Ta is largerthan a reference gradient Tas stored in the control unit 120. Where thetemperature drop gradient Ta is larger than the reference gradient Tas(namely, if YES), the procedure returns to step S95 because the internaltemperature Tr of the refrigerating compartment 24 is being normallylowered during the rapid refrigerating operation. The procedure fromstep S95 is then repeated. On the other hand, when the temperature dropgradient Ta is determined at step S102 as not being larger than thereference gradient Tas (namely, if NO), it is determined that therefrigerating compartment evaporator 40 has been frosted because theinternal temperature Tr of the refrigerating compartment 24 is beingabnormally lowered during the rapid refrigerating operation. In thiscase, the procedure proceeds to step S103. At this step, it isdetermined whether or not the drive time Cr of the refrigeratingcompartment fan 44 counted by the timer included in the control unit 120is more than a predetermined time Crs (a predetermined rapidrefrigerating time of, for example, about 2 hours) stored in the controlunit 120.

When the drive time Cr of the refrigerating compartment fan 44 isdetermined at step S103 as being less than the predetermined time Crs(namely, if NO), the procedure returns to step S95. The procedure fromstep S95 is then repeated. When the drive time Cr of the refrigeratingcompartment fan 44 is determined at step S103 as being more than thepredetermined time Crs (namely, if YES), the procedure returns to stepS104. At this step, the control unit 120 applies a control signal forstopping the rapid refrigerating operation for the refrigeratingcompartment 24 to both the compressor driving unit 150 and therefrigerating compartment fan motor driving unit 162 of the fan motordriving unit 160.

Based on the control signal from the control unit 120, the compressordriving unit 150 and refrigerating compartment fan motor driving unit162 stop the compressor 56 and refrigerating compartment fan motor 42,respectively. As a result, the rapid refrigerating operation for therefrigerating compartment 24 is completed.

Thereafter, the procedure returns to step S105. At this step S105, thecontrol unit 120 applies a control signal to the refrigeratingcompartment heater driving unit 132 of the heater driving unit 130 inorder to execute the defrosting operation for removing frost formed onthe refrigerating compartment evaporator 40.

Based on the control signal from the control unit 120, the refrigeratingcompartment heater driving unit 132 drives the refrigerating compartmentevaporator's heater 47. Accordingly, the frost formed on therefrigerating compartment evaporator 40 is removed.

While the refrigerating compartment evaporator's heater 47 is generatingheat, the temperature of the refrigerant passing through therefrigerating compartment evaporator 40, that is, the conduittemperature P2 of the refrigerating compartment evaporator 40 is sensedby the refrigerating compartment conduit temperature sensing unit 142 ofthe conduit temperature sensing unit 140. The resultant data from therefrigerating compartment conduit temperature sensing unit 142 is thensent to the control unit 120. This procedure is executed at step S106.At step S107, the control unit 120 then determines whether or not theconduit temperature P2 of the refrigerating compartment evaporator 40 ishigher than a predetermined temperature Ps (namely, a defrosting endingtemperature) stored in the control unit 120. When the conduittemperature P2 of the refrigerating compartment evaporator 40 is lowerthan the predetermined temperature Ps (namely, if NO), it is determinedthat the frost on the refrigerating compartment evaporator 40 has beenincompletely removed. In this case, the procedure returns to step S105.The procedure from step S105 is repeatedly executed until the conduittemperature P2 of the refrigerating compartment evaporator 40 reachesthe predetermined temperature Ps.

On the other hand, when the conduit temperature P2 of the refrigeratingcompartment evaporator 40 is determined at step S107 as being higherthan the predetermined temperature Ps (namely, if YES), it is determinedthat the frost on the refrigerating compartment evaporator 40 has beencompletely removed. In this case, the procedure proceeds to step S108.At step S108, the control unit 120 sends a control signal to therefrigerating compartment heater driving unit 132 of the heater drivingunit 130 in order to stop the generation of heat from the refrigeratingcompartment evaporator's heater 47.

Based on the control signal from the control unit 120, the refrigeratingcompartment heater driving unit 132 stops the driving of therefrigerating compartment evaporator's heater 47, thereby stopping thedefrosting operation of the refrigerating compartment evaporator 40.

Thereafter, it is determined at step S109 whether or not a predeterminedpause time (namely, a predetermined delay time (for example, about 10minutes) for protecting the compressor 56) has elapsed after thedefrosting operation for the refrigerating compartment 24. Where thepredetermined pause time has not elapsed yet (namely, if NO), theprocedure from step S109 is repeated until the predetermined pause timeelapses.

Where the predetermined pause time has elapsed (namely, if YES), thecompressor 56 can be driven again. In this case, the compressor 56 isnot damaged because it paused sufficiently. Accordingly, the controlunit 120 stops the defrosting operation for the refrigeratingcompartment 24.

On the other hand, when the refrigerating compartment 24 is determinedat step S99 as not being under the defrost requiring condition (namely,if NO), step S111 is executed. At step S111, it is determined whether ornot the drive time Cr of the refrigerating compartment fan 44 countedduring the rapid refrigerating operation is more than the predeterminedtime Crs (namely, the predetermined rapid refrigerating time of about 2hours) stored in the control unit 120.

When the drive time Cr of the refrigerating compartment fan 44 isdetermined at step S111 as being less than the predetermined time Crs(namely, if NO), the procedure returns to step S95. The procedure fromstep S95 is then repeated. When the drive time Cr of the refrigeratingcompartment fan 44 is determined at step S111 as being more than thepredetermined time Crs (namely, if YES), the procedure proceeds to stepS112. At this step, the control unit 120 applies a control signal forstopping the rapid refrigerating operation for the refrigeratingcompartment 24 to both the compressor driving unit 150 and therefrigerating compartment fan motor driving unit 162 of the fan motordriving unit 160.

Based on the control signal from the control unit 120, the compressordriving unit 150 and refrigerating compartment fan motor driving unit162 stop the compressor 56 and refrigerating compartment fan motor 42,respectively. As a result, the rapid refrigerating operation for therefrigerating compartment 24 is completed.

Although the fourth embodiment of the present invention has beendescribed in conjunction with the rapid refrigerating operation for therefrigerating compartment 24, it may be similarly implemented for therapid freezing operation for the freezing compartment 22.

Industrial Applicability

As apparent from the above description, the present invention provides adefrosting apparatus for a refrigerator and a method for controlling thedefrosting apparatus, wherein the refrigerating compartment is cooledirrespective of the internal temperature of the freezing compartmentwhen the internal temperature of the refrigerating compartment is higherthan a predetermined temperature, so that the refrigerating compartmentis maintained below the predetermined temperature. In accordance withthe present invention, the defrosting operation is carried out inaccordance with the drive times of the compressor and refrigeratingcompartment fan when the internal temperature of the refrigeratingcompartment is higher than the predetermined temperature even though thecompressor and refrigerating compartment fan are continuously driven.Accordingly, it is possible to improve the cooling efficiency. Inaccordance with the present invention, the point of time when thedefrosting operation begins is determined on the basis of the drivetimes of the compressor and refrigerating compartment fan and thevariable environmental condition. Accordingly, the defrosting operationcan be efficiently achieved.

Where the defrosting operation for the refrigerating compartment isachieved within a predetermined time under the defrost requiringcondition of the freezing compartment, the defrosting operation for thefreezing compartment is delayed so that the defrosting operations forthe freezing and refrigerating compartments can be simultaneouslycarried out. On the other hand, where the refrigerating compartment isunder the defrost requiring condition, the defrosting operations for thefreezing and refrigerating compartments are simultaneously carried outirrespective of the defrost requiring condition of the freezingcompartment. In this case, the refrigerating efficiency is improved.

For the rapid refrigerating operation, the point of time when thedefrosting operation for the refrigerating compartment begins isaccurately determined by calculating a temperature drop gradient on thebasis of a variation in the internal temperature of the refrigeratingcompartment. For the rapid freezing operation, the point of time whenthe defrosting operation for the freezing compartment begins isaccurately determined by calculating a temperature drop gradient on thebasis of a variation in the internal temperature of the freezingcompartment. In either case, accordingly, it is possible to efficientlyachieve the defrosting operation.

Having described specific preferred embodiments of the invention withreference to the accompanying drawings, it is to be understood that theinvention is not limited to those precise embodiments, and that variouschanges and modifications may be effected therein by one skilled in theart without departing from the scope or spirit of the invention asdefined in the appended claims.

We claim:
 1. An apparatus for defrosting a refrigerator, comprising:arefrigerating compartment for storing food to be refrigerated; afreezing compartment adapted to store food to be frozen, the freezingcompartment being defined above the refrigerating compartment by anintermediate partition member; a compressor adapted to compress arefrigerant to that of high temperature and pressure under a control ofcompressor driving means; a pair of heat exchanging means respectivelyassociated with the freezing and refrigerating compartments and adaptedto heat-exchange flows of air, being blown into the freezing andrefrigerating compartments, with the refrigerant, thereby cooling theair flows; a pair of fan means respectively associated with the freezingand refrigerating compartments and adapted to supply the cold air flowsheat-exchanged with the heat exchanging means to the freezing andrefrigerating compartments under a control of fan motor driving means; apair of heating means respectively associated with, the freezing andrefrigerating compartments and adapted to defrost the freezing andrefrigerating compartment heat exchanging means under a control ofheater driving means; temperature sensing means adapted to senserespective internal temperatures of the freezing and refrigeratingcompartments; temperature setting means adapted to set respectivedesired temperatures of the freezing and refrigerating compartments, thetemperature setting means also setting a rapid freezing operation and arapid refrigerating operation; control means adapted to determine thepoint of time when a defrosting operation for each heat exchanging meansbegins on the basis of a drive time of the compressor and respectivedrive times of the freezing and refrigerating compartment fan means; andconduit temperature sensing means adapted to sense respective conduittemperatures of the freezing and refrigerating compartment heatexchanging means during respective heat generating operations of thefreezing and refrigerating compartment heating means.
 2. The apparatusin accordance with claim 1, wherein the freezing and refrigeratingcompartment heat exchanging means are a freezing compartment evaporatorand a refrigerating compartment evaporator installed at the freezing andrefrigerating compartments, respectively.
 3. The apparatus in accordancewith claim 1, wherein the freezing and refrigerating compartment fanmeans are a freezing compartment fan and a refrigerating compartment fancoupled to rotating shafts of freezing and refrigerating compartment fanmotors, respectively.
 4. A method for controlling a defrosting operationof a refrigerator, comprising:drive time calculating step of calculatinga drive time of a compressor and respective drive times of freezing andrefrigerating compartment fan means; defrost requiring conditiondetermining step of determining respective defrost requiring conditionsof freezing and refrigerating compartment evaporators on the basis ofthe drive time of the compressor and the drive times of the freezing andrefrigerating compartment fan means all calculated at the drive timecalculating step; defrosting operation step of executing a defrostingoperation for removing frost formed on the freezing and refrigeratingcompartment evaporators in accordance with the defrost requiringconditions of the freezing and refrigerating compartment evaporatorsdetermined at the defrost requiring condition determining step; anddefrosting and determining step of sensing respective conduittemperatures of the freezing and refrigerating compartment evaporatorsbeing varied during the defrosting operation executed at the defrostingoperation step, and determining whether or not the frost on the freezingand refrigerating compartment evaporators has been completely removed onthe basis of the sensed conduit temperatures.
 5. The method inaccordance with claim 4, wherein the defrost requiring conditiondetermining step comprises the steps of determining the defrostrequiring condition of the freezing compartment evaporator on the basisof at least one of the drive time of the compressor and the drive timeof the freezing compartment fan means, and determining the defrostrequiring condition of the refrigerating compartment evaporator on thedrive time of the refrigerating compartment fan means when the freezingcompartment evaporator is determined as being under the defrostrequiring condition.
 6. The method in accordance with claim 4, whereinthe defrosting operation step comprises the step of simultaneouslyexecuting the defrosting operations for removing frost formed on thefreezing and refrigerating compartment evaporators when the drive timesof the freezing and refrigerating compartment fan means are more thanpredetermined times respectively stored in the control means inassociation with the freezing and refrigerating compartment fan means.7. The method in accordance with claim 4, wherein the defrostingoperation step comprises the step of executing the defrosting operationfor removing frost formed only on the freezing compartment evaporatorwhen the drive time of the refrigerating compartment fan means is lessthan a predetermined time stored in the control means in associationwith the freezing and refrigerating compartment fan means.